I'm no expert, but there is more to it then just heat energy, A lot more. From what ive seen, many front mount turbos dont spool for shit. So whats the problem, they should have a bunch of heat right ?
Corky Bell explains it much better than I could. I suggest you pick up a copy of his book "Maximum Boost". It is a must read for anyone doing custom turbo work.
BARNES & NOBLE | Maximum Boost: Designing, Testing, and Installing Turbocharger Systems by Corky Bell, Bentley Publishers | Paperback
My point that you seem to have a hard on about is that a rear mount system will never be as responsive or trouble free as a front mount. And it wont. It's called the laws of physics. There is more air to push, more restrictions and more parts to fail (namely the oil return pump). StckJk hit the nail on the head, when was the last time you saw an OEM rear mount turbo ? .... Never.