Ok here is another question if all your stages are bottom mount, are you limited to just two bottles? Or how do you fit a third? Like two AL80s and a AL40 O2 bottle?
what
@rddvet and
@kensuf I WANT to be able to top mount because the profile is better and I had things hanging below me, but it just doesn't work. I've tried everything, helped optimize some of more prominent methods of top mounting, but I just don't like it, so I bottom mount.
In cave diving, you get to cheat which is nice. My deco bottle/s just get nose clipped to a butt rail/hip d-ring, etc. and dropped off. They don't have to look good on the way in because you aren't carrying them very far. IF we take a third stage which is a safety bottle when scootering, it is butt-mounted and trails behind. It goes away in the slipstream of the diver when on a DPV, and you can grab it with your thighs to keep it well mannered. It's annoying with nitrox when full, but it's tolerable.
We dive LP121's to get rid of the quantity of stages, and anything more than 2 stages for penetration is done on a CCR. If you have to carry more, dive doubles or a rebreather where you have a lot more real estate available. If you need to do the dive on sidemount for whatever reason, do a setup dive and drop the deco bottles and at least the first stage then you can use a leash when picking them up on your way out.
Sidemount really is not the answer when you need more than 4 bottles though, and you should seriously consider alternate configurations. I also believe that CCR's are far safer when you are getting that far back in a cave because they buy you time to solve problems that OC simply can't do.
If you're doing double stage dives, I'd recommend leaving a 4-8lb clip weight in the deco room with your O2 bottles so you can clip all of the dead stages off when you get back. Deco on those dives is long but not distinguished, so having the clip weight to get rid of all of the bottles is really nice. Use the leash and then when you're ready to come up, you just grab the weight and bring it up with you.