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When opting for doubles, the issue is to pay attention for the total weight to wear outside the water, as you have two bottles and eventually (due to the extra volume) need also to add weight (depends on whether you opt for steel or CarbonDive bottles in your doubles set).
I was using steel HP 120s, and I was trying to learn to use a dry suit and a BP/W, all new, as well. Maybe it was all of those factors combined, but I felt like they were throwing me around. I made the mistake of tightening my harness much too much to try to deal with that.