Per Wilko:
From someone who's also outside the normal sizes (XXL-Tall): I've
started using microfleece shirts instead of my old Helly Hansen thermo
shirts. Different brands give them different names, mine are from Hiko,
but I bet you can find them in U.S. brands as well.

They are at least as warm as fleece, but don't absorb as much water, and
I stay a *lot* more warm when wet than when wearing normal fleece.

Just drove up to a nearby REI store (camping/hiking/outdoors
stuff) and checked out what they had.

They had a house-brand micro fleece, and even had a few pullovers
in XXL... but they were cut wrong for paddling - not enough
freedom in the shoulders.

But at the same store they had a rack of "Mysterioso" tops.

Turns out my assumption about Mysterioso was wrong. I must've
been looking at an ad for some specialized subset of the product.
Plain old Mysterioso, seems like PolarTec except that it's much
more "open" weave-wise. Also the shirts were raglan-cut at the
shoulders for freedom of motion. Only problem was they didn't
have XXL, much less XXL-Tall.

I think I'm shopping for a Mysterioso pullover in XXL-Tall now.
--
PeteCresswell