I love VHB tape. I recently started using it in some designs. It is marvelous. I am using the 15 mil VHB to bond polycarbonate sheet to aluminum. The 3M FAE (tech rep) says that this stuff starts to bond correctly after 15psi is applied for one second. Full strength develops in 72 hours.
I wonder if you could use 1/2" tape for the ridge line, and 1/4" wide tape for the hem? This stuff is amazingly strong. I have only experimented with small amounts so far. A long seam does look like a challenge.