Questions on frame bending

Thanks guys.
As far as adjustment goes, I'll probably have the wheel as far back as it will go and have a tensioner of some sort. I was going to change to horizontal dropouts but ran out of steam at this time. There are tons of fiddly details to take care of so it can wait.

Up and down adjustment is controlled by spacers. There are four spacers two top and bottom that can be juggled around to change the height of the caliper. In and out is adjusted by spacers against the bracket. I lucked out and found a piece of 2mm flat bar rather than stacks of washers.