Remember, if adjusted properly per Torklift instructions, there is only about 300# of force on the tie down.
On my light 815, I run much less, probably only about 100# of force. When adjusted per Torklift, I was bowing the bottom in the area of the anchor point. The 815 only has a 1.5 x 1 piece of wood they pull against. At least though it is a metal bracket that catches the top.
I would not be worried about damaging the tubing, but would be concerned with fatigueing the welds at the joints next to the tie down bracket.
