In the last 3 years, I've been through (personally owned) the following. All diving in ~40-50F water (Vancouver Island) year-round. Ranking how long I would
comfortably dive in each of those combos in winter (~40F water):
- Fusion one-piece 45 mins
- 4th Element Arctic 2-piece 30 mins
- 4th Element Halo AR 90+ mins
- Santi Flex 2.0 (heated) 90+ mins
- Santi/Avatar fleecy one-piece undersuit 60 mins
Out of all of these, the highest-mobility are the Arctic 2-piece and the Santi/Avatar fleecy 1-piece. In general, warmer undergarments are bulkier and give less mobility - although a lot of this is due to the drysuit as well. My old drysuit was a close cut, and I couldn't easily fit a thick undergarment underneath.
What I would suggest trying is seeing how restrictive your undergarments are without the drysuit on top - the undergarments I've had that were more restrictive (the Fusion and the Flex 2.0) were also more restrictive outside of my drysuit. If you can move easily in the undergarments alone, and move easily in your drysuit without the undergarments, then I suspect the suit is just a little too small for that thickness of undergarment.
In terms of recommendations - I really like the Halo AR, I find it just as warm as a used Santi BZ400, but with better gas management and venting. I actually dive the Santi/Avatar fleecy all-in-one (which came as a package with my Avatar suit) most of the time (especially in summer), as I find it dives even better; it's just not quite warm enough for longer dives or in the depths of winter.
