A couple of comments and medium-baked ideas;

1) The adhesive on 3M's Dual Lock is especially good, unlike most
velcro you find in stores. Dual Lock *should* stay stuck even in a
hot environment. You might troll the 3M site for temperature specs
(they mention aerospace).
2) I bolted my GPS antenna under the glare screen (which is not
mounted to the canopy). To allow for break away in your situation you
could use nylon bolts instead of metal bolts. To really make sure
they break away, you could remove some concentric material (cut a
groove) around the bolt near the head. Removing concentric material
is what is done for break away mounting of, for example, runway
lights.
3) Double stick tape? That should break away. But might have the
same temperature issues. Again, stick with 3M branded.

Good luck, John