I'm only 6' tall, but it seems to me that most tents (and high end camping equipment in general) are built around people of fairly small builds.
For what you're asking for (space), get a 4-man tent like the bigger REI domes, Kelty or North Face domes, things like the Eureka Timberline4. The GoLite Shangri-la 5 picture above is massive, and I'd love to own one again, but I too find freestanding designs to be of importance. I currently make do with a walmart Ozark Trail 7x7 tent and sleep diagonally, they make a 9x7 version for a few dollars more that might fit your bill. Or learn to carry less stuff and make do with a smaller tent.
The largest tent I would tour solo with is what I have now. Easy to set up quickly, cheap to replace, and durable. Plenty of room for me and my gear, and could probably easily fit me and my girlfriend if we were ever to ride on a trip together. More isn't always more though, and it depends on what you mean by 'tour'. Going from campground to campground, state forest or the like, week after week, I'd keep what I have. Moving more off-road and remote, I'd move towards a bivy and tarp particularly if solo. Moving towards having a base camp and exploration, I'd move bigger... to a cabin tent and or an RV.