Lately there have been really good deals on doubles wings floating around, like dive rite rec wings and (I think) classic for about $160 new. Since you have heavy tanks, get an AL backplate for about $60, harness stuff for another $40 and you're not spending much more to get the BP/W than the zeagle BC.
I'm still confused about your statement about using zeagle tech BC "with backplate". Unless I'm missing something about that particular BC, it's either the BC or the backplate, not both together.
As has been stated, you need a dedicated doubles wing for the dual 104s. You might go for the classic wing, it's huge IMO but they call it a medium-to-large wing. I'm using a rec wing, which is substantially smaller, for my double 72s and I think it would plenty for larger cylinders. Once you get stages, etc you might need more, I guess. In any event, if the zeagle tech bladder is a "crossover" type made to sort-of work with singles and doubles, chances are pretty good it won't work well with big doubles.
I'm kind of in a similar situation as you. I'm using doubles for recreational diving in 25 ft of water, often while DMing, solely because I want to train with doubles for eventual cave training. I'm enjoying it and getting more fine control with the doubles all the time. You'll like it, except for carrying the tanks around on land.
