How best to increase driver leg room?
 

I'm 6'5" tall and have decided I need to increase my driver's side legroom in my 2006 F150 FX4 extended cab PU. I've unbolted the seat and determined another 2" of legroom would resolve my issues. Unfortunately, just relocating the seat bracket mounting holes 2" further back is not a simple matter given the configuration under the cab.

Has anyone altered/relocated their driver's seat to increase legroom and if so, how did you do it?