You have an unwinnable challenge on your hands. The smaller rivers that you mentioned are best suited non V boats, the Columbia on the other hand can kick out some nasty water fairly fast and a V is needed. Also the heavier the better for that rough water which a sled is not. Probably your best bet for under 10,000 would be an older Alumaweld Super V with a 3-6 degree at the back. Also...stay away from rivets (my opinion) If you had more money to spend there is no doubt I would send you to Thor-built and have them custom make you one...but that would ding you for about 30,000.00 Email me if you have any questions.

Jim