I dive single LP 85's now and have the desire to explore some of those deeper wrecks up here in the great lakes.
Many divers start by doubling up tanks they already have, e.g.
RonFrank:
A lot of my friends stated with double alum 80's and went from there. If you have some singles this is a fairly cheap way to go.
I happened to have two HP 120s and doubled them up as my first set. From there, I added some used HP 100s, and a couple of sets of used AL80s, and finally put together a set of new HP130s. If I came across a good deal on some LP tanks, I would probably add a set of those as well. Basically, there are a variety of doubles sets you can use, and there will definitely be an element of personal preference which you will find for yourself as you try different sets. For example, I slightly prefer the bouyancy and trim of my AL80s, followed by my HP100s, plus I can dive either set wet if the occasion allows. The 130s are good tanks in the water (although a bear on the shore because of their weight). The 120s are a bit long / tall for me and I end up somewhat 'foot down' with them. If you have LP85s and like them as singles, start there and see how you like them as doubles.
The other possibility to consider if you want more gas for deeper wrecks, is setting up a sidemount rig. I won't say it will be less expensive than backmount, but it may be an attractive alternative configuration, at least for shore diving.
I'm not sure if I will go technical or rec. with doubles. Before I decide, I'll try my LDS set-up in the pool to see what doubles are like, but I would also like some direction from some experienced double divers on this form.
Setting up backmount doubles initially requires a bit of assistance from someone who knows how to assemble them, e.g. your LDS. Diving them is a matter of practice, a) getting used to the extra weight and change in trim, b) acquiring certain safety skills (valve shutdowns as one example) and attitudes, and c) recognizing that the extra gas can easily help you get into an unintended decompression obligation. From that perspective, there is some merit in pursuing technical training, even if you don't plan to do a lot of deco diving on those wrecks, so you are prepared to use your doubles safely and effectively. I dive doubles almost exclusively, and most of the dives are recreational (i.e. within NDLs). But, technical training provided the skill development opportunity that allows me to do so, plus I do have the option for longer, deco dives if I want. However, I started diving doubles before I pursued technical training, so the training is not necessarily a
pre-requisite.
I also don't want to break the bank doing this switch from singles to doubles.
Others have commented on the Hollis package, specifically the harness. I would not pursue it, either - neither simple nor easily adjustable. One question is, what do you dive now with single tanks? Since you were looking at the Hollis package, I presume it is not a BP/W rig. As others have suggested, a simple (SS) BP with a plain vanilla web harness is a reasonable starting point, and not as expensive as the Hollis unit. (The Hollis wing seems like a good deal at the quoted Scuba Toys price, though.) I have a number of backplates, SS and AL, and only bought one of them new (for my wife). Only one has a 'commercial' harness (bought used, with a plate). The rest of the harnesses I set up myself. Since you are diving the Great Lakes, I presume you are either diving dry, or using thick neoprene, so a SS BP would probably be a best first choice. I would add that, diving dry, I find it helpful to have a quick release sewn into my harness on one side, to make it easier to get out of the rig after a dive.
. I also love my Halcyon Evolve 40 lb wing, Al backplate & simple webbing harness.
