I bought a SOL Escape Bivy. Breathable, emergency, space blanket stuff. It zips part way down, breathes great, is warm down to about 50 degrees, weighs 8oz. I like it, it performs as advertised but...I'm on the large size especially my shoulders and it's a little tight. I mean I planned to stuff a 45 degree bag inside and it's tight when I do that. So...I want to make it bigger. I bought a second one and a longer zipper. My plan is to split it open and replace the zipper with the longer one and splice in a piece of the extra bivy to make this one bigger. I got some 3M 77 spray adhesive and I got some sissors. Any pointers, cautions or suggestions on the seams???

I would recommend thinking about using some tape to reinforce those new seams. Get pics, glhf!