ORIGINAL: jester_s1
Yes, on the heat issue I see scale modelers sometimes having to go to great lengths to keep things working here in Texas. The exit hole needs to be at least twice as big as the intake, and in some installations modelers need to build baffles to direct the air straight to the head. Adding some extra natural castor to our fuel can also help, as can running a little rich with the resultant power loss.
The OP didn't mention the plane he has but I think you hit pretty much all the bases. When I tune someones engine for them this time of year and it's flying along at mid throttle and just quits it often just needs to be richened up a bit. When a plane has been stored for a while and it keeps cutting out mid flight it is usually a bad line. This time of year I see a lot of engines that tend to over heat mid flight when they are tuned correctly on the ground. It is a wonder what just changing a glow plug can do too. When I pull down an old plane and start running it up I do as you mentioned and only fill the tank about 1/4 or so just to make sure my lines are OK.