I’ve done 4 “parabolics” now. I glued all of them up with polyurethane glue (Gorilla Glue or Elmer’s). As long as you’re careful and don’t get it on the deck or bottom, it doesn’t show up too much after shaping. You can tape up your edges if you like but just being careful applying the glue worked for me. Do a search for “Drewtang.” He’s probably done more than anyone on here using high density foam rails (at least that post their stuff that I’ve seen) and has some really good looking boards.
My technique is to use the cutoffs to aid in clamping, using bar clamps to put it all together. Sorry, not a very good explanation, pictures would explain better!
Here’s an attached photo showing the glueup (sort of). A bit of the tail didn’t hold real well so I put the rail cut offs back on and reglued and clamped that section. Just gives you an idea of the clamping process.
Best piece of advice I got from Sway’s (in the archives) was to only cut one side of your outline, use offcut to clamp (a la surfthis) wait to dry and then repeat for other side. sounds like twicw as much work but makes the glue up a lot easier and cleaner. Craftee is right, there is tons of this in the archives.
If you use a heat guy on the divinycell you will be able to bend it around much tighter corners. Just put the rail in place, start bending in and heating the hard to bend places, and then let it cool in place.