im 6'7" and ride a 1980 cb650,got the same problem,it feels like i got my knees next to my ears..
im planning of moving the footrests forward,somewhere around the front of the pipes,and im in process of making it a bobber,with a single seat,that will be backwards more...
now for a 750 this might be different,but raising the seat might offset your point of gravity and change the behavior of the bike...
lowering the pegs might be giving you trouble with ground clearances of the pegs in corners..
how about what you see on a cafe racer,where they move the pegs more to the back..
not really an answer,more brain storming along with ya..