Adding a backplate to the SMS 75?

[OperationZulu]

I currently dive with hogarthian aluminum BP/W with a 30lb donut bladder and STA. After about 5 years of abuse, the thread on the bladder has finally crumbled and I now currently find myself in the market for a replacement bladder. For some time I had also been thinking about adding the OMS profile to my rig to give me a very quick side mount option but I have not been able to find a supplier with stock. I may be stupid, but I can’t even seem to find them on the OMS website? Replacing the bladder and adding the profile would set me back in the region of USD250.
With this in mind, I recently came across the Hollis 75. I was told by the owner that she managed to get it for USD499 and could not speak highly enough of it. It looked like a pretty decent piece of equipment but even on the face of it I had a few concerns/thoughts

1. The harness system looks overly complicated. Reading around I see most people claim this helps with out of the box adjustments, ready to dive in 10 minutes blah blah. Given I already have a nicely fitting harness that I have been using for years I am not sure all those plastic toggles etc are a benefit to me. It just looks like more stuff that might break?
2. The harness seems to be made up of quite a number of separate sections. Follows from above, I would prefer the simplicity of the single piece of webbing I currently have on my backplate. The Halcyon webbing is soft enough that I do not experience the digging or cutting into the lower back so many people complain about.
3. Obviously, as designed for SM, the corrugated inflator hose is located on the lower left hip. Does anyone know if this can be interchanged with the dump valve on the top left hand side in the event you wanted to dive single back mounted?

Basically I think my first question is as follows: Can I do away with the harness of the SMS 75 and mount it to my current back plate and single webbing harness? If possible, with the ability to switch position of the dump valve and corrugated inflator hose, I think this would become a very flexible and versatile rig for me. Do Hollis sell each element of the standalone? Or do you have to buy the entire rig?

My second question has to do with the bungees on the SMS 75. I understand the bladder used on this is exactly the same as the SMS 100. Therefore, if you remove the bungee from the top half of the wing, and had it placed on a back plate, you should theoretically get the same lift capacity of the SMS 100 which could be effectively used, say for doubles?

Before answering please understand that I am aware of the other hybrid options on the market (UTD etc) and I am also aware that many view you either make a commitment to a dedicated back plate wing set up for singles/doubles or you buy a dedicated SM system like the Razor. I am asking the questions above because I want to tailor the rig to my specific needs and am interested in understanding whether anyone has made the modifications to the SMS 75 I am talking about above. I don’t seem to be able to find any resources. Thoughts very welcome!

 

[tbone1004]

we'll go through this point by point

The OMS profile was made by the old OMS, they essentially went out of business and while the name and logo remain, the only product that they kept were the Slipstream fins. Everything else is replaced. The OMS profile is also not a great sidemount rig.

1. The SMS75 was designed for Florida cave diving. In sidemount there is almost never any weight placed on the harness, so the buckles are not liable to break. IF you do walk out with the cylinders clipped to you, all of the weight is on the front d-rings, so the front straps are in compression. Since webbing can't go into proper compression, the buckles can't break. I don't necessarily agree with their placement, but it is does greatly expedite adjustment and doesn't really detract from anything with the harness design. If they removed the quick slide buckles, then adjusting the straps with slide locks would take forever. Is it a benefit to you once you have it adjusted and if you only dive in one exposure suit, probably not, but if you really don't like them, you can cut them out and replace with a piece of webbing.

2. the harness for sidemount is not the same as a one piece harness. The dynamics of sidemount are very different from backmount, so the same rules don't apply. If you want a one piece harness, or as close to it as you can get, the Razor and xDeep stealth are essentially one piece harnesses. The digging and what not is not going to happen in sidemount because you aren't carrying 100+lbs of doubles. Very few people carry bottles into and out of the water on their rigs, they usually carry them up on their shoulder one at a time.

3. yes it can, but you do not need to. Just run a drysuit inflator hose instead of a short inflator hose and it works just fine. Did it for many years when diving backmount doubles or singles on my Nomad.

Question 1. No and you would not gain anything by doing it. You need the SMS plate to keep the wing in check for sidemount diving and you gain nothing by adding a plate to it. You can swap dumps and inflators on any wing out there, they use the same flanges. In a sidemount wing with the wing restrained, there is no advantage to swapping them back to have the inflator on the top for backmount. The corrugated hose is far too long, is usually clocked 180* from where it needs to be, and the pull dump on the exhaust valve is far too long. Leave it in the position of your primary use, and adapt from there for the secondary. You can buy replacement wings, and harnesses, but the wing will not work properly under a backplate.

Question 2. You understand wrong, it is a completely new design, albeit very heavily based on the SMS100 with modifications that were done by Edd Sorenson at Cave Adventurers.

Question 3. I would love to answer you, but you don't actually tell us what your needs are. Do you want a singles rig that you can dive sidemount in? If so, then that really doesn't exist because what makes a hogarthian singles rig a hogarthian singles rig, greatly conflicts with sidemount. Sure you can make it work, but it won't be a hogarthian rig anymore because you have to restrain the wing and do a bunch of other goofy things to make it work.
Do you want a sidemount rig that has the ability to dive singles? If so, then the SMS75 will do that out of the box, just put cam bands in the cam band slots and put the tank on your back. Use a drysuit inflator hose instead of a wing inflator so it can come under your left arm put and connect, and you're good to go. You may have trim problems being head down because you just moved your CG towards your head and all of the lift in the SMS75 is at your butt, but if you're a good diver, you can make it work.
Do you want a sidemount rig that can handle singles and doubles? If so then the 75 will be able to handle small doubles in a drysuit, and the Nomad XT and SMS100 can handle big doubles, singles, and sidemount. Again, you will have trim issues in all of them, especially with doubles, but it will work.
If you want a backmount rig that can do doubles, but also do sidemount in a pinch, that is easier because you can figure out how to get the doubles wing on the inside of the backplate, but it won't work for singles, and is really not the best idea for sidemount.

You have to answer my question above, before we can help you.