Not so dramatic with petrol but was immediate cracking and failure of the part, not so much crazing.
Yes, tried down to about 10-15 deg, same result with failure at the point of most stress.
This morning I cut some bits of polycarb and .016" ali and riveted them together in various configurations and poured a small amount of thinners on each.
Firstly I made a multi rivet test, with two rivets through 1/8" holes- no extra clearance,
then two rivets with 1/8" hole in the ali and 5/32" clearance hole in the polycarb,
then two rivets with the clearance plus a nylon washer under the rivet head,
and one unriveted hole for control, no photo of that one but it had no cracking. So you can see all of the the rivetted holes had some cracking but the clearance holes were the smallest and least cracked, so I did some more tests with single rivet pieces with a clearance hole and destressing them with the heat gun for vaious times. Heat gun was on high setting, 150-200mm from piece, waving across piece not concentrated blast, and I allowed the part to cool to room temp befor applying the thinners.
first, heating for 1 minute and as you see not one crack. Encouraged by the result I tried several more individual tests with varying heating times and found I could destress the rivet penetration with as little as 15 sec waving the heat gun over the part. Lowest time I did was 7 sec and the thinners produced 2 small 1 to 2mm cracks.
So from these test I reckon next time i rivet in a polycarb window i will drill clearance holes and spend a small time destressing with the heat gun.
Cheers
Rick