This is my mounting solution for a generic pull-down projector screen of the type you'd find in any office supply store. Key objectives for the mount was that it had to blend in with the casing of the screen, allow the screen to be easily removed and relocated when required, and be sturdy enough to handle repeated use. The screen is primarily held in with gravity, with a little help being given by the screws on the endcaps which hook into a rim at the back and provide enough resistance to keep the screen from bouncing free when it's retracting but not enough to permanently lock it into place (at least so far.) The weight of the screen is primarily being supported by the metal case so as to reduce the risk of the plastic endcaps cracking over time. This does mean that the bracket extends somewhat into the screen's retraction slit, but I believe I've left enough room and angled the corners enough to reduce the risk of it chewing up the screen's edges over time. They're also reversible, so you can have them secured either in front of or behind the projection surface.

I printed my prototypes in PLA+ using a .6mm nozzle, 4.5 perimeters, and generous amounts of infill. This actually seems plenty strong to me but the remaining ones I plan to print will be done in PETG for added strength and durability. No supports are required when printed in the provided (recommended) orientation. 

Mounting is handled via 4 drywall screws drilled either into studs or anchors. My recommendation would be that you snap the clamps on the end of your screen, get a buddy to help you lift and level it, then drive screws in through the upper holes to secure the brackets. Once that's done you can pull the screen out and do the bottom holes so that you don't need to worry about the brackets twisting out of place.