Don is spot on about the reason for the rings in your dry top neck and wrist seals.
I should have gone into more detail about what they really do. The technique I described is the way the Drysuit mfg. taught us to do it if it was needed and with my neck it was
I would have passed out if I didn't trim
I am down to the next to last ring on my drytop and it is still snug when I put it on.
Remember to use a spray to keep them soft and from cracking, after rinsing I do mine once a month if you paddle on the Platte it wouldn't hurt to do it more often. Don will get you the right stuff...