I'm 6'2" and regularly fly both the legacy RV-12 and new RV-12iS models. It's tight to be sure.
As others have mentioned, be sure you have the correct seat cushion (maybe consider getting a custom one.) I've noticed if I fly with a really old cushion I have more head clearance.
Also, The flap on the seat back can be lifted completely clear of the mid fuselage brace so the seatback is actually as far back as it can possibly go.
The legacy -12 uses a simple piano hinge riveted to the seatpan. You could rivet the hinge farther forward than standard to sit in a more reclined position. Maybe more headroom there?
Last solution: build an RV-14