I'm not a canard owner, but I've had a chance to climb into a few.... Thought I'd pitch in with some comments about the back-seat, since that's where all of my time has been.
I am 6' 1" and weigh just over 200 lbs. I have only sat in a Long-EZ on the ground; but it was just fine for space. These planes are small and fit like a glove - so when I say "fine" I mean enough room for my hips, shoulders, knees, etc. to avoid being pinched. The difference between the Piper I've flown in and the EZ's is like the difference between a Minivan and a Corvette. OK, so the EZ is probably more comfy than the Corvettes I've been in - but being a licensed race-car driver, I have the experience to make that space-comparison with authority. ;-)
I've flown in a nicely-built VariEze, and it was OK. The fuselage had been built an inch or two wider than the plans - and that was a GoodThing(tm) for me. Without that extra inch I would have been squeezed a bit. As it was, the VariEze had enough room for me to sit in and that's IT. I wasn't wedged in, but there was no room to shift about or flail my arms. Of course, I had so much fun with the stick in the back seat that I didn't care; but a long flight would've gotten to me.
The biggest issue for a tall guy like me in the back seat, is the leg-room. My knees were just rubbing the seat in front of me; and my legs were slightly tucked underneath me because the seatback goes to the floor (thus requiring the tips of my toes to be behind my knees, when viewed from straight above). On my short 30-minute flight in the VariEze, again I was having so much fun that I could ignore it... But anything more than about 2 hours of that and I would have been in pain. I'd say I was at the cut-off for size and weight, for the back-seat of a VariEze. The Long-EZ was slightly more forgiving, but not by much.
One final note: I had never flown in a plane as light and small as the 620 lbs. VariEze... Initially the feedback on the ground from the asphalt, and the wind on the takeoff roll, were somewhat disconcerting (additionally, I was trusting my life to the building-skills of a man I had just met). If you have a spouse or significant other that you're trying to get to fly with you - prepare them for that and make sure they have confidence in you and the plane; and your first flights will go a lot smoother. ;-)
Just my amateur $0.02...
--Noel