I have not done a conversion to a Y stern, so cannot give an opinion. But as to the difference between a side mount, and mounting an outboard to the centerline, I can.
Ran a side mount for several years, with only one involuntary dismount. Finally got a chance to buy a square stern, and haven't looked back. It's not a wide transom at all. It is a full flat transom with no Y shape at all. I can't measure it now, as its in the country, about an hour away, but the transom can't be more than 10"s, 12" at the most. Sort of a middle between a Y, and a normal wide square stern.
From a balance perspective, having the motor on the centerline makes all the difference. I paddle my square stern more than I expected to, as I use the motor as a back-up, more so than primary propulsion. Don't think I would enjoy paddling a wide transom. I realize the trade off in efficiency, with a transom rather than a traditional stem, while using a paddle. But as you stated, for wind or current, my little 2hp does great. And I have a small bit of security, knowing that if compromised on a solo trio, whether a broken bone, health issue, or whatever, that I could get to either cell phone coverage, or at best, an area where assistance could reach me. I turn 67 in a couple of weeks, and have realized that I am not as bullet proof as I once was. I still use my other canoes, but there are certain times that having that little 2hp, or a trolling motor (with a cut-down shaft) get the call. I do love the silence of electric for day trips and fishing.
I would think a small 6" transom would give you the ability to mount your 2hp kicker, with only a small trade off in paddling efficiency.
Looking forward to seeing what you decide to do.
Best of luck with it.
Bill
