Just out of curiosity- how is HydroSkin intended to fit? I used the sizing guide and I am in the middle of the intended size But when I put it on I can hardly move my arms. The arms are skin tight and I mean tight. Does this stuff stretch out after a period of time?

When wet
I found mine was much looser when wet.

It fits like a wetsuit
You don’t want water flushing through your top. It will stretch and loosen up as you wear it. If you absolutely can’t move your arms without resistance then it might be too tight. If you have never worn a wetsuit, I suspect it’s just fine.

Mine is tight
and you will feel a little resistance until you get used to it. Get out there and flex those muscles - I’ll bet its fine.