Thanks all.
This is just the advice I was looking for.
I just ordered some 4 oz fiberglass to cut strips on the bias.
I too have used the "masking tape, cut it while it's soft" method. Works great.

When I made my Great Auk 6 years ago for the inside seam I used glass that I cut (bias) myself. A bias cut unravels less than a straight cut. I have no memory of how that inside seam went. (I was of the opinion at the time (uniformed stupid opinion) that I could just hide my mistakes with more epoxy, which is why that kayak weighs 75 pounds).

I have a roll of 2" fiberglass tape, with the serious ridge problem. I wasn't sure if it there were any tapes that didn't have this problem. Apparently not. I wonder if it's wide enough to use for the inside seam? I think Nick recommended 2" and 4".

"Selvage" -- thanks for the correct term. Having just the right word solves a lot of Googling problems.

I have a Fiskars roller cutter. I couldn't get it to work on some 6 oz E glass. Based on your recommendation, I'll give it another go.

Thanks for all the excellent and helpful advice.

Will

Paradise is an island with kayaks, fast internet, UPS and a table saw in the shade.