I dont use the 6" long bits. I buy standard length and then use an extension. This way I have both lengths for the price of one. This is what the bit looks like. It is clog free for aluminum. I would also use cutting wax to help keep it from clogging.
I rotated the TB, but it was a lot of work filling in the radius to get it to flow into the first runner. If you dont have a tig, and dont know how to build aluminum up with a tig, I would say dont do it.