I have to say I'm surprised to hear these discouraging words about the Radisson. I bought one in a yard sale a year or so ago (for $150 US!) and like it a lot. I don't have the sail kit, sadly, but it is the 13.5 foot with the square stern, foam lining, oar locks and whatever you call the foam on the gunwales. The finish is birch bark.
I haven't had much chance to take it out yet, but a few times on a local lake. I have to agree that with me alone, the wind does make it hard to handle with a paddle, but I bought a 54lb electric motor and with the battery up front for ballast, it handles beautifully and zips right along. I haven't done much colliding with underwater objects, but having read the comments, I'll be careful.