: anyone have any experience, thoughts, rantings about 4 mm hull glassed on the
: outside, versus 3 mm hull glassed on outside and inside (3.5 oz on
: inside)?

Both sound light. Watch out for wear and tear inside the cockpit if you
have no glass over the floor - epoxy can wear through with sandy feet,
(so can glass - but it is a lot more obvious that it is starting to
happen). Reinforcement over the keel maybe a good idea, depending on how
you choose to abuse your boat.

: the permutations are endless

Indeed - I glassed the hull of my hybrid Cormorant with 4 oz down the sides
and over the chines, then with 6 oz over the keel and up over the chines,
and with tape over stem and stern, which had ash laminations externally
over the 4 mm ply. Inside hull is 6 oz between the bulkheads, and 4 oz
at the ends. Even with a stripped deck (4 oz inside and out), this is
still the lightest kayak I've handled at 16 kg (but I haven't ever seen
anyone else's stripper or S+G )-: I can vouch that it stands a lot of abuse
fully laden rock hopping round western Scotland in a swell, though I've had
to do some remedial work on the corners at the bottom of the stem, and
around the edges of the skeg box - sharp corners wear quickly, especially
on a concrete slipway (a landing error, I think ...)

Andy