I was curious about the griots so checked and you can indeed use a 6" pad. It really depends on the size of the backing plate. The 6" griots is actually has a backing plate less than 6". For safety reasons, you want the backing plate to be smaller than the pad.
I like 5.5" too, but if the griots has enough power for the 6" pads, I'd invest in 4" in pads and 3.5" backing plate if you want options.