no not at all
single blades work fine if the boat is designed with a narrow gunwale station like the RapidFIre is.
Most “pack canoes” have flare all along the hull rather than shouldered tumblehome so your assumption is mostly true. Hornbecks do not have shouldered tumblehome.
The Rapid is only 24 inches wide at the rails. Using a 46 inch Fox Works bent shaft is fine. The other hiccup of course is that it can be hard to find stock bents that short.
The Canak still has lots of deck and a what appears to be a heavy seat.
RF paddle
Since I race, train, and recreate in several types of canoe, GRB (Grasse River Boatworks) has made paddles for me in every size from 48 to 54 inches. They will make any length you want.
I often use the RF as a training boat when unable to train with my voyageur race team. With my high seat RF I prefer the 49 inch over the 48 or shorter bent shaft. It gives me more reach on the catch, and the critical first foot of pull better simulates my bow position when racing in the voyageur.
I paddle the RF in 3 different modes, all with a high rail mounted seat. Race rules require a double blade paddle in the RF class of boats. So if I am training for the 90-miler RF class for that year, a double is what I reluctantly train with.
When training for voyageur class races (especially the Yukon races) without my crew, I paddle the RF with a either a 49 or 50 inch carbon bent shaft. I detest hit-and-switch every 6-8 stroke paddling necessary when solo racing (in voyageur marathons we hit-switch approximately every 80 strokes), so my RF stroke is a rapid semi-pitch-semi-J-semi-C that works very well for me at a race pace with that paddle length.
When recreating I prefer a straight long blade feather edge custom wood paddle from Tremelo, otter tail or willow leaf blade shape with a nice palm grip. I enjoy the multiple types of linked strokes and maneuverability it allows. When cruising I mostly do the Canadian stroke. At the end of the Canadian, a slight wrist twist literally flips the paddle out of the water for quick recovery to the next entry. At slower speeds I like the box or Indian stroke that only a thin edge straight blade paddle can do.
Canak
The Canak seat is mounted on the standard Wenonah adjustable solo seat mount. It looks heavy but is not and in fact is the most comfortable tractor seat I’ve sat in. One’s bottom is about 5 inches or so from the floor. I’m 5’10" and use a 52" Mitchell bent shaft with no problems, though I’m considering a 50". The boat also paddles well with a double blade, I like a 240cm, but I feel it’s really set up for a single. I love my Rapidfire, the sports car, but the Canak is a great SUV. You should paddle one if you get a chance, it’s difficult to judge a boat by looks and numbers as been proven here time and again.