Dave,
i have quite a bit of hands-on experience with panel adhesives (3M and Fusor mainly) from my former career as a body tech and can tell you they work great for what they were designed for......that is external panels only (no structural panels, i.e. intrusion bars, supports, ect are to be "glued") and dont try to use filler over glued exterior seams (like sail panels)...the glue expands and contract differently from the fillers and you'll end up with cracks along the seam line (per the manufacturer), ya gotta weld those seams! Surface prep is very important, grind the mating surfaces with 80 to 36 grit to give the glue somthing to bite on and clean with a fast evaporating solvent like laquer (sp?)thinner.

The shear tests done by 3M are pretty impressive and i belive the delamination temp is around 600-800 degrees..so if you screw up all you have to do is get out the heat gun and take it off!