Sorry, my memories might be wrong, I tried to remember to the scene with Bolg and Azog meeting each other at Dol Guldur, and I had the memory of Bolg being slightly higher than Azog, but you might be correct and perhaps it is only a question of the camera angle. Anyway I see absolutely no reason to make Bolg to a normal sized Lego fig. He should be same sized as Azog with the same kind of head set-up. This kind of Bolg would be a big disappointment.