I think the UV break down is going to be your enemy with any product. With that said Zip Tape is pretty freaking amazing. I would use it for a million projects if it wasn't so pricy. I haven't found anything it wont stick to yet.
From a contractor. It's not a house so I wouldn't get too crazy. Flash the sides first and then top with Zip or Pella tape. leave the bottom open for drainage (always). Then I would trim it out with composite (PVC) 1x4 and seal the edges with OSI Quad Max. Spray foam the inside with great stuff window and door.