Looks like a great project. Will you make another for the challenger?
The joints look great and your approach is sound. I am currently working on mortise and tenons for the back legs of a pair of chairs with carved wooden seats. The mortise will be hidden and attached with glue and a long screw. The front of the leg is tapered about 2 1/2 degrees to the seat surface. The edge of the leg to seat joint will show and the rest of the shoulder will be fussed over with chisels to get a solid fit.
I try to stay away from the shoulder edge to prevent slight damage to the surface grain. Did you have any problems with protecting that edge as you pared away?
Rustic? Well, no. That was not my intention!