I can think of only two reasons to install a rear turbo: not enough room to put it near the exhaust manifold and because race car.
The closer the turbo is to the engine exhaust, the better it works. That's
Physics. Sure, a rear-mount will work and well enough for most "casual" drivers (and it does look pretty cool, IMNSHO) but, if you're worried about optimal performance, you gotta be hot.