I might as well post what I sent to scooteri as an IM response:
scooteri,
I used to add a third "drop-in" style seat to a tandem & try paddling from the center. That didn't work so well; it's simply too wide to permit effective stroking. I did the same thing with a seat/yoke that was "reversible". Even though it sat me higher, permitting an easier reach, I found I could not grab water well with the paddle. Also, stroking from the center is simply not as effective as from either end due to the shape of the canoe.
I've also tried paddling from the reverse position in the bow. db uses this approach, if I recall correctly from when he joined my party on Beaverhouse a few years back. It worked well for him and I guess it was ok for me when I threw a pack in the opposite end of the canoe for counter-weighting. Frankly, my favorite approach paddling solo in a tandem is to sit in the stern facing the way I'm supposed to face and simply load up the front end of the canoe accordingly. I've done this in my Souris River 17 footer many times and get by fairly well except when I can't avoid strong sideways winds.
Yet another approach I've used with a tandem involves a "rowing rig". I bought one from Spring Creek Outfitters years ago. The big downside of this is you spend your time facing backwards the whole way. An upside is that the craft is stable as hell IF you lock your pontoons on correctly. I could also pretty easily keep up with most tandems using my 9 foot oars. Of course, another BIG downside was that I had to disassemble the rowing rig to get through most portages. Come to think of it, that's probably why I targeted Cirrus Lake when I travelled with that rig; very FEW portages and those were almost "highways".
Now, you ask my preference? Well, I guess there WAS a reason why I finally purchased my Wenonah Prism.
I guess I simply wasn't convinced these other methods of soloing were as effective as they could be. I took the plunge & bought the Prism.
The Prism took some getting used to. Initial stability is unlike the tandems I've been in. Until you get the vessel moving, it tips fairly easily. Also - and this is a MUST - you have to learn how to load the Prism correctly given wind condition. Going "bow-heavy" in a tailwind nearly sunk me on lake one, day one last year when we first launched into Woodland Caribou Park. That was carelessness; I knew better but let myself get hurried. On the other hand, loaded correctly, I have found the Prism to be exceptionally good-handling in the wind, particularly in a headwind. It's also offers decent stability for fishing though not nearly what you might be used to in a tandem.
I'd recommend practicing in a solo canoe such as a Prism before committing to paddling one for an entire trip. They do take some getting used to. After a few times out in one, you'll get comfortable. I've used mine over the past three years or so & have been very pleased. I mainly paddle with a bentshaft single blade but I also carry a 9 foot double-blade for when I want to cover water fast. When conditions get surly, however, it's my trusty bentshaft that I grab.
Due to center-seat placement, the portage yoke arrangements in some tandems can be tricky. I did not like the removeable thwart bar portage yoke that was initially offered with my Prism. It tended to slide around on me while carrying. Instead, I purchased an expensive aluminum portage yoke that locks onto the bars of my slider seat. This solved the problem & worked just fine.
I'll be in the stern seat of a tandem for my trip to Woodland Caribou this July. The numbers worked out that way.
That's all I know to tell you about my experience. Again, with a little practice time in advance, I'd opt for a solo canoe such as a Prism every time.
Good luck with your decision!
Jimbo