There is no problem with overheating on glow fuel, unless you are using high nitro fuel.  The problem is lack of lubrication with lean fuel mixtures.   If you convert them to gas they will operate at much higher temps without any problems, except perhaps a few with small fin areas.

There are perhaps a few exceptions to the above.  For example a Fox Stunt .35 may overheat with a lean run with moderate nitro because of its very small fin area.