Hey Greg:

My wife and I built a CLC 16LT for her last year and it
came in at 43 lbs. We used 4mm throughout and did nail
on the deck. This was our first boat so we probably
used more epoxy than necessary and didn't trim the shear
clamps at all.

About 6 months later I built a Cormorant (16'3" x 22-1/2")
for myself and it came in at 37 lbs. There were advantages
to building my wife's boat first!. I did round off the shear clamps
on this one, was much better at using epoxy (especially in
the filets), and used screws to attach the deck. I think
experience played a role in getting the weight down.

35 lbs. is probably quite possible with 3mm plywood, but
you definitely sacrifice some strength. Whether that's
critical or not I don't have enough expertise to comment
on.

Never got around to posting a picture of the Cormorant on
this BBS, so I'm including a link now. BTW, we love both
our yaks.