Given your location I'm going to guess that the wood of choice is WRC. You should be able to get that in any length you want. Because you'll be cutting it into strips, absolutely clear wood isn't necessary. Strip builders usually look for flat sawn wood so that when they cut strips they wind up with quarter sawn grain.

I have a little bias on strip length because when I ship wood I keep the length to 8 feet to keep costs down. But when I build in my shop I use strips from 8-12 feet in length. It's nice to have a couple of boat-length strips for critical elements like sheer strips. I scarf joint two shorter pieces on the bench when I need a strip like that.

For general stripping I really think it's easier to to use shorter strips. Boat length strips are awkward to handle and require you to fit both ends and get the length spot-on in order to fit. I like to fit one end of each strip amd overlap them in the middle. Then I make a wood glued scarf joint with a dozuki saw. A butt jont would work just as well.

Mike Scarborough
Friendship Kayak