The alternator is in the stock location but I think you hit on what my thought was.
The length of the belt between the crank pulley and the alternator. That is the only thing I can come up with.
I have tried to find a deep pulley for the alternator to see if that helps but haven't had any luck finding one.
I am looking into a tensioner on Mancini Racing but I'm not sure if it will fix the problem.
The pic I posted is not a good shot but you can see the location of the alternator.