i ride lefty first, so I kick with my right, it's a lot more natural to me. I've tried front foot but yeah it is awkward.
The one thing I've noticed about kicking is that when you are first starting it takes a lot of time to get used to the height of the mountainboard and finding the right distance to kick at so your foot doesn't hit the back wheel. I've done that soo many times and have even wiped out from curbing the back of my ankle with the back wheel. It comes at a suprise, especialy if you are going fast... heh.