A friend and I made a different style ultra lite raft out of Cuban Fiber and a Cuban Fiber adhesive tape. The raft went together well, weighed 8 ounces and held air nicely for a while. the problem we ran into is the tape let the fabric bond creep when under pressure. It was a slow process but the raft failed in a short time on the water. I would test to be sure the tape you plan to use will hold as well as a fabric weld, which I think it will not unfortunately. Do some tests with scraps of fabric taped together and sheer force pulling them apart.
Mike