NWCWdiver:
Are they neoprene or latex seals? Neoprene neck seals need to be stretched (NOT trimmed), usually over a tank (AL80), coffee can or some other round object of the appropriate size. I did mine using a coffee carafe. If they are latex seals, they need to be trimmed. However, if you're trimming your own seals, you need to be very, very careful or you can trim them too much or leave kinks that can easily tear.
Did your suit not come with a manual? I have the same suit and it came with a very detailed manual covering this. If you don't have a manual, I'd recommend either a drysuit course of the book Dry Suit Diving: A Guide to Diving Dry, 3rd Edition by Steve Barsky, Dick Long and Bob Stinton.
