Not true have dived my rEvo extensively in the tropics in 3mm wet suit, during courses etc, trims out fine, and is most certainly very usable.
Another rEvo myth, which i heard when I was looking the revo back in 2012, there is no risk at all of moisture that may ordinarily accumulate in the inhale lung damaging the cells should one turn on their back.
i have totally flooded my rEvo (my mistake, left DSV open a crack when practicing bailout) filled it the brim only noticed when my cells started going berserk , got home rinsed out the unit flushed cells with fresh water and they were fine, cycled them out of the unit as normal over the next few years.
I already answered on another forum but I will share some info from my early days.
We I first got my rEvo and found myself butt heavy, I merely added 4 pounds of weight to the top tray and my trim was as close to perfect as it has ever been. I could hover 1 inch off the sand and remain perfectly horizontal without any need of movement at all. I really wish I could still do this but now I fight it just like everyone else. From day one, every other rEvo diver was bitching about how they were to heavy and could not add any more weight. I just assumed they were idiots and were afraid to try. When it was time for a new wetsuit was when my perfect trim went away forever. I went from a 3mm to a 5 mm and now I was too heavy in the water AND my feet were sinking. I went back to my old suit and everything was fine for the test. Turns out that the custom made suit from Wetwear being made from rubatex is much more buoyant than even a 5mm suit. All those other "idiot" divers were right all along and I was just lucky to have the wetsuit I did.
I still have the 4 pounds on the top tray but I am over weighted in the ocean with a wetsuit. I could really use at least 2 more pounds up there. I have even considered the idea of just adding neoprene "leggings" to my wetsuit.
I have decided that the only way to make it work properly is to get a titanium unit which is light enough that I can make up the difference by adding weight to the top of the unit. Or just dive a drysuit all the time.
The most overlooked thing that will give a false sense of being butt heavy is having too much loop volume. Doing this will cause a huge swing in center of balance with just the extremely smallest of head up movement, your feet will drop like a rock and the fight begins.