I'm 6' 3 1/2" on a good day and have found my newly built RV6A a bit cramped. It took a while to get used to this "feature". Most of my flying is not GA airplanes but military transports, a way different perspective. I felt this the most on cross country flights (1.5 hrs to the Big Island) with a passenger during the first 60 hours or so. I think now I have adapted. BTY, I never noticed this doing touch and gos or flights in the practice area.
My RV has a center throttle quadrant which decreases leg freedom of movement, it would be better like some RVs without a center consol. Also I find the electric flap housing makes using my kneeboard difficult with my right hand. Most of my height is in my legs, but I couldn't see moving seat too far aft as my back wanted a good backrest angle.
I put my rudder pedals pretty far forward, but honestly this probably doesn't matter much as my feet are off the rudder while flying XC. Sometimes I tuck my toes under the pedals at altitude to stretch a little. Not a problem with size 11 sneakers.
My canopy is raised in the rear about 1/2", but again probably inconsequential. Most headroom gained is from correctly sizing the seat cushion. With my headset on and sitting with good posture I gave myself about 1/2 to 1 inch of clearance from the top of the canopy, that way with my normal slouch, I've got more room.
I have the seat foam from Van's with the fancy blue astronaut foam which is very comfortable and without pressure points--important when you can't move around too much to stretch.
Last advice: Don't worry, with age you'll shrink and have more room.
Hope this helps. Aloha. Greg