-- Last Updated: Oct-01-12 9:21 PM EST --
In "most" situations, "most" people won't be worried about capsizing. You didn't indicate whether you might be a really large person (some people really are too big for average solo canoes), but if not, odds are good that you will soon get over any fear of simply capsizing. It's also worth noting that the first thing everyone with time spent in rec-style kayaks does when getting in a decent solo canoe for the first time is wonder "how is this thing going to stay upright?" Your boat is SUPPOSED to be a little lively underneath you, NOT rock solid. You'll come to appreciate that aspect. Also, that shallow-V hull that Mad River uses tips off-center a bit more easily than a shallow-arch, but then gets firmer pretty quickly as you lean even more.
I'm in about my 8th year of solo canoeing (not just occasional outings either) and still haven't flipped without a really good reason (except for practice sessions where I tip over intentionally). In fact, I've flipped exactly twice in all that time (and the first time, there was a "good reason" considering that I'd had just a few weeks of experience, but would be a "bad reason" if it happened to me now), but if I paddled a lot more frequently in challenging (to me) whitewater than I do, I'd have surely flipped more than that. Anyway, if you can be comfortable kneeling, I am pretty sure that you won't be "falling over" unexpectedly. In flatwater or mild whitewater paddling, your biggest risk of capsize is when getting in or getting out of the boat, and your feet won't be under the seat at those times. Oh, but see Kim's post below, and note that if you push the envelope in free-style, you'll find plenty of excuses to tip over in flatwater too (I don't imagine that's high on your agenda right now!).
It's getting late in the year for playing around in the water, but given the nature of your question, I would recommend that at some point you intentionally flip the boat a bunch of times to get the feel for it, and to practice getting your feet out from under the seat once you are upside-down. Turning your body alignment a little sideways happens pretty naturally when the time comes, and your feet will come out easily in that case. In the meantime, make sure your seat is as high as you want it to be, and work on getting comfortable with the feel of the boat and how it responds to being leaned.
Finally, there can be risk associated with having your feet under the seat in strong whitewater. Lots of people use a saddle (pedestal) for that kind of paddling. Though most do it primarily to provide better boat control, it eliminates the risk of foot entrapment too. However, if you aren't paddling that kind of whitewater, a saddle is probably overkill. In fact, I recommend against using a saddle for any reason except difficult whitewater. The flexibility in "seating" (which of course includes kneeling) and other aspects of body position is one of the real advantages of a standard bench seat. With a bench seat, you can position yourself off-center if you wish (being off-center even by a tiny amount is not an option with pedestals or bucket seats), and you even have a choice of several different foot and leg positions when kneeling, let alone all the additional options that become available when one or both knees is NOT planted on the floor. With a pedestal, you'll be pretty-much stuck with exactly ONE option in body position. On an all-day trip, having choices in body position is wonderful.