It would be tight but could work
I'm 6'5" and 250lbs and fly a 7A. I'm getting along fine. I made a couple of accomodations. The biggest thing I've done is to lengten the strap connecting the rudder pedals to the cable. This gave me a couple of extra inches. Luke at Classic Areo is manufacturing a "tall pilot" model of his Sportman seats that will give me an extra inch or two. There is also the option of moving the seat-back attach point back an inch or two. I tried that in a 6 and it was ok but then, of course, you sit more upright.
The canopy height is just barely ok. I use Bose headsets. If I wear a baseball hat under the headsets, I occassionaly bump up against the canopy. Without the hat, it seems fine.
6'7" would be a close fit but the pleasure of flying an RV is such that I would encourage you to give it a try. Fly one long enough -- at least a short cross country -- to get a sense of how it would feel on a real trip. Check into the modifications I just mentioned and investigate what else might be possible.
Again, I'd give it a try, for me it has been worth the effort.
Ed