Hey, a thread with my name on it!

Yeah, you can replace the center THWART with a seat. But as others have
noted, you actualy don't want to be in the exact center of the canoe
when you paddle, as the boat will tend to pivot rather than move
forward when you stroke. Unfortunately, the center thwart DOES want to
be in the exact center, so replacing it with a seat is at
cross-purposes. For this reason, the middle thwart seat in 3-seat
canoes is actually for a third person, not a solo paddler. Even
traditional kayakers sit a little behind the midpoint.

What most folks do is sit backwards in the bow seat and paddle the
canoe the other way. If you find that you cannot get close enough to
the center for your liking (and you are unwilling to admit that its a
style problem, not a design flaw), then try replacing the second thwart
with a butt board. The second thwart is the one behind the bow
paddler...it lies about halfway between the middle thwart and the bow.
In some boats its in front of the stern paddler, but not commonly.

A butt board is a piece of 1x3 that is on hangers so that it sits a bit
lower than a thwart, and it doubles as a seat and a thwart. It is
angled at 30deg, so when you are kneeling and putting your butt cheeks
on it, it doesn't dig into the back of your legs. If it is placed
right, its actually VERY comfortable. You can put some padding down for
your knees, wrap some ensolite around it, and spend all day on it with
no problems, as most of your weight is on your butt, no your knees.
I've seen folks put a flat part on the top for an actual seat, which is
cozy.

I'll see if I can find some pics of what I'm talking about. I have a
rudimentary one on my BlueHole that I regularly used to spend a week or
more 10-12 hour days on with no problem. I even removed the other seat
from my boat to better place the butt board.

Or you can just learn to paddle solo the way most solo boaters do. :-)

--riverman