RE: Servos in the engine compartment?
Yep, that's one example of some cases we can't separate the way the mfg's suggest.
Still, we should strive to do so IF we have the room.
My GP Ultimate (27.5%) has tons of room to separate everything and I've done so. Same with my SD-260 (30%).
But my H9-Twist-150 has everything crammed close together. Simply wasn't room to do properly.