With the shipping 3.21 firmware Stryd data just cuts off to zero after a few minutes (a known 955 bug by the looks of it) and it seems TruSync / Primary Training Device is broken (not supported) as my HRV etc didnt carry over so I have 3 weeks to wait for HRV status etc
Also I am finding optical HR really quite poor so far, although I usually get bad results with optical I wanted to see if it had improved but on a walk HR was droppping close to my Resting HR at times!! I had on another watch on the opposite wrist with a chest strap and the 965 was often 15 bpm lower than actual. I do know how to wear my watch correctly and too be fair these poor results are typical for me. I hoped a lighter plastic body might improve things there, but no luck.