RE: Are Hitech servos problematical with Futaba 2.4Ghz
First off, the Futaba receiver that had a heat limitation of 60-degrees C. was the original R6014FS receiver. The new, R6014HS receiver, and all of the other FASST receivers did not have such a limitation. The R6008HS receiver certainly doesn't have that limitation.
As far as non-Futaba servos working with one of the Futaba receivers in high-speed mode, we can only say that we don't know about specifics. There is no list of non-Futaba equipment that may or may not be compatible. Checking with the maker of the non-Futaba equipment would be the best way to go. In your case, Hitec should be consulted to see. We've not had any specific complaints of modern, digital servos having any difficulties. The operating difficulties with the R6014FS receiver came with older servos designed before the R6014FS receiver was designed. None of the other Futaba receivers had any particular difficulties with properly-designed non-Futaba servos/accessories.
Again, while there is no list of compatible or non-compatible items, we've not heard of difficulties with modern non-Futaba equipment operating with Futaba equipment.