im not sure a front mount would be more efficient but you will prob get better results from a front mount.
Im getting one as i do a LOT of motorway driving and the debris would just destroy it, whereas with a top mount your safe, plus i have a bit of a penchant for rare items and also you get to have the name ARC under your bonnet. All tarty answers but it fits the bill for me.
As for heat soak im gonna be using a nitrous cooling bar and throttle switch, im pretty sure that when needed, it will make the intake charge cooler than that of a front mount.