Hi Dave-

: 4) With the standard 6 oz outer layup on the outside, can I get by with 4 oz
: on the inside of the hull?

To save weight, I was thinking the same thing. Nick's book, The Strip-Built Kayak, (our web host here, Guillemot Kayaks is run by Nick Schade) suggests however that fiberglass works most effectively in tension, and (as I read it) that because of this it might be better to save weight by using lighter fabric on the OUTSIDE rather than the inside. He does some tests that show how panels are stronger and resist impacts better if the heavier glass is INSIDE. (p.110 ¶3) It also stands to reason that the wear & tear that the inside gets from sandy feet or shoes is more intense than the gentle pasage of water past the hull.

: 5) can I use 4 oz on the inside and outside of the deck?

Nick does suggest the deck might be a candidate for lighter fabric, but also mentions (elsewhere) that sometimes people have wet exits. They end up scrambling back aboard over the deck, and this can be rough on the lighter layups.

: I am using 3/16" strips and its alot thinner than that in some areas,
: like probably 1/8" so I want to avoid as much oil canning as
: possible. The boat will see some action on the rocky shores of Lake
: Superior

I've been out on Lake Superior. Steep, closely spaced waves can develop
very quickly, along with exciting summer events like 50 knot thundersqualls with hail. We actually had the hail come first in a dead calm, and a half-inch was on deck before the wind arrived to blew it all off in about three seconds. Others may be able to tell you how much weight you'll save by using 4oz cloth, but I'd opt for stronger on the Big Water.