Bisping could never make 170 imo, he looks like a skinned rabbit when he makes 185. Paul Harris could make 170 easily and id still think he would be a powerhouse, He would certainly have the big risk factor for GSP with his explosive grappling but i think GSP would jab his way to UD as always.
Bisping is 6ft 2ins, same as Silva.
The Smaller MW's tend to be around 5ft 11 - 6ft 0, 6ft 2 is the high end of the scale, bare in mind Bisping was once a LHW, no chance does he make a healthy 170lb.
There is a very good chance Palhares could be the smallest MW fighting in the UFC division, just quickly looking and 5ft 8ins at MW is going to take some beating there are a few 5ft 11 in there and thats the next closest I have been able to quickly find.