Scott,

I can’t think of a good reason to add strength to a boat simply because plane edge strips were used rather than cove and bead.

As for the inside, you could save a little weight by using Kevlar, but I wouldn’t get too concerned about needing additional strength. If you want to use a tight weave, and end up with around 6 oz. of glass on the inside, consider getting a bunch of the 3.25 you mentioned and put on a couple of layers. There are two main reasons to go that route. One, as John pointed out, lighter weight fabrics are easier to work with, particularly when using tight weave styles. Two, 6 oz tight weave (crow-foot or harness satin) is not particularly common. Most suppliers have 3.2 oz. and 9 oz., but not 6 oz. in those styles. I used stitched biaxial on the inside of one boat, and would not do it again.

Sam