Nick I'll be honest with you... I'm scared to tell you to destroy your screen! Before cutting painting (as some people recommend) or doing anything that would/could destroy your commercial screen, see if you can sell it and put that money towards your new screen.
I would think the method I'm working on would also work since I'm using BOC, but I don't know how delicate your screen material is. I really wouldn't want to tell you to cut the screen material off and then ruin it and end up throwing everything out. If you can't sell it, or feel your won't get any money out of selling, sure then take a gamble.
I'm still working on this but my first prototype worked and now I just need to make a few updates, take the photo journal, and then put it all together as a thread.
I know you don't want to wait for that though
Okay here's what I am doing... Most people make a wood frame and then stretch and either staple or tack the screen material to that. There is nothing wrong with that method at all. Basically it's following the principles of what artists do.
Here's what I'm working on... I got screen door aluminum frame, cut everything to size, and then instead of staples or tacks, use spline just like you would do for making a window screen.
Now here's the problem, but only a minor one... When you get to the size of a projection screen, that's usually way bigger than any screen window or door and the frames need some cross braces. You can buy clips easy enough, but they cause the cross braces to be pressed against the screen material. This is fine if you're making a screened in porch, but not so fine if you're making a projection screen. Since I already had my prototype frame material (bought everything at Home Depot for around $20) I decided to just buy some 1/8th inch thick by 1/2 inch wide aliminum and rivited that on the back of the screen frame as cross braces. Now one thing to keep in mind, and that is this isn't the whole screen, it still will need a trim border. Weight wise though it weighs next to nothing and pretty much will be as heavy as whatever you make your black border out of.
Now if I didn't already have the framing I have... I would go this route...
Connecticut Screen Works has a wide variety of screening frames, but check out their screen wall systems... no center supports needed! These are extremely strong and can be made insanely BIG!
They also sell thicker and stronger regular screening frames that's less expensive.
What I like about this aside from the weight is with spline, you can change your screen later on without having to pull staples or tacks. That may not be an issue for most people because most don't change screens that often, but some may want to upgrade screens. For me it makes it light so I can take it up and down and put other screens up for testing.
This 'should' work for you, but like I said, don't destroy your screen unless you really want to rip it apart. You don't have to use a DIY screen with this, you could get some Da-Lite material and that should work. I'd see if you can sell your screen and put that money towards your new fixed frame
Another option is aluminum extrusion that has a 'T' molding slot. Some extrusions are rounded or arc'd and look very nice and just like some of the commercial screen frames. Instead of spline, you'd use T molding with it. You can wrap the frame in velvet, or if you want Flock it with velvet and it will look just like a commercial screen frame. Flocking would be more time consuming though.
Bottom line is it can be done, just think about it before you destroy something you might be able to get some money out of...