My brother's next door neighbor flew F-4 Phantoms with the Texas Air National Guard. One of his flying buddies was flying an F-4 when the guy in the rear (WSO?) punched out. He said the plane was almost unflyable and he considered punching out himself. Of course, I've seen a lot of models lose canopies and continue flying with no apparent adverse effects.

I know all about the heat. My local club had Big Bird Flyin last Saturday and I had problems and ended up working on planes all day and then when I started loading up to go home, I nearly went into heat exhaustion. It took me over an hour to load up when it usually takes about 20 minutes. I fought muscle cramps for over an hour after I got home.
Hope I don't ever do that again!