Rear engine over heating is not really an issue as long as proper (and normal) cooling precautions are taken on real hot days. It may cost a bit more, but running a bit more fuel through those engines can really make a huge difference. You will find it ¡s even less of an issue if your engines are inter-cooled which I highly recommend.
Having flown several hours in a Super Skyrocket, with the entire new engine compartment baffling and the additional rear engine cooling duct, that engine actually now runs cooler then the front engine! Go figure!
Rick