I have 1 first stage and 2 seconds for myself or buddy. No different then any other OW diver.
I dive quite often with the same setup Tegg has. I still use my full OW reg setup and have everything still rigged the same way as I would with a full BC on. The power inflator and SPG hoses are just strapped to the tank with the tank bands, with the SPG being in easy view of when I look down at it. The 2nd-2nd stage is still wrapped over my shoulder and on a necklace, and my primary 7ft hose is still coiled around my neck like normal too.
I absolutely LOVE the freedom of movement with this setup. Easier on the back, easier to move your head/shoulders around when looking around. The lower profile makes for much quicker movement and swimming is more streamlined and effortless than with it on my back.
The only downside is:
1 - some boats don't like SM, so I bring along a little plastic backpack w/the same style harness (no BC still) for boat diving.
2 - really rough surf conditions (yellow flag or higher) for shore diving make getting out of the water a pain sometimes when you're trying to unclip the tank while holding onto your fins, flag, and any other gear (scooter, lobster gear, etc) while getting pummeled by large breaking waves. But that's what your buddy is there to help you do
I dive with Tegg quite often in this configuration and have grown to like what it offers. So much so that I built my own monkey rig and learned to dive with it. Getting used to it took all of 5 minutes. You just really need to be comfortable with your buoyancy is the only trick.
Unless I absolutely need my backplate/wing setup for some specific type of dive, I'll use my monkey rig harness as much as possible.
As to the OP... call the dive operator, some don't mind, some will grumble about it, but will still let you on (tip them more if they help you with your setup though since it's not normal on boat diving). Some will flat our refuse though.... so just call around until you find one that doesn't mind what you are wanting to do. BTW, dive what everyone else on the boat is diving. Dual tanks is pointless unless everyone else has them. I've been on one charter before where they let a couple guys diving doubles just keep diving during everyone else's SIT time... while we were on the surface, they continued to follow the guy's flag and picked them up at some point while we were on our 2nd dive. But that was arranged ahead of time they said.