Well, I got some nice 1/2" rod and had a friend weld a 1/2" bit on to it.  Should have gone larger on the bit, but I didn't think of that.
So I drilled through it, first with a cordless Ridged Drill and then a 110v Makita Hole hawg type of drill.  
I was not too far off, but not good enough.  I realize the 6x6 is not going to be big enough anyway.  I played with the large bore cutter and the amount of material left is just not enough.  A friend has a surplus piece of 8x8 PT, so I will try again on that.