Photo Background Bracket (with adjustable braces)

I was inspired by a number of other stands that did the same thing, but I found the one problem with all of them was, if your paper/card stock was not sufficiently thick or ridgid, the whole thing was unstable. So I decided I needed to build in some bracing, but also have it removeable if you needed. And then I relaised it needs to be adjustable - so here it is - the everything model. The front channel will hold paper or cardboard (possibly vinyl but I don't have any handy) and the back/bottom channel is 3mm to use thin MDF (fibre/craft wood) if you need a more rigid background. My thinking was if you need tp photograph something tall, use the brace on the bottom and stand some MDF in the back and then have a tall piece of card stock resting up the MDF. It is about having options. Also, because you can set your braces to the same width as the paper, the paper can just rest in the grooves, so you can have different colours in the top and bottom half of the curve, creating a false ho