I don't know if that would hold up better in the long run than normal lumber. This material is straight as an arrow in stores, so that is the allure for me.
The OP could "Try" though, and if it works out it might be a very neat solution. It certainly will not warp...ever...and if adequately braced, the degree of pull pressure stretching Spandex across such a frame should not make to flex enough to be any concern.
Still, ripping would require the use of either a Table Saw with a special Blade, or a Skill Saw with Rip Guide and the same Plastic Cutting Blade (120 Tooth)
Then there is the Mitering of the Corners, and needing to use both adhesive and counter-sunk screws. The use of Simpson Strong Tie "L" Corner and "T" Braces would be strongly advised no matter what.
Seems like a lot of potential issues await, no small degree of uncertainty of success, all coming at more expense overall
To quote James T. Kirk;
"I'm laughing at the superior intellect"
I am definitely concerned about the strength of the product over time; it seems like it would eventually bow from the lack of strength.
I am interested in using aluminum, however where can you get in such large pieces without going to an industrial supply house?
Honestly since my hybrid alum-wood screen has seasonal humidity issue, using this instead of wood would have been the ideal case for me, as the alum sq tubing is the structural member.
I wanted my border to be very rigid along the skinny length so it would be easy to mount a straight line, but flexible to easily conform to my curved laminate screen.
After trying many-many moldings at HD/Lowes, I settled on this "Tuf Board", it fit all my rqmts perfectly. Easy to cut, can be routered for inside bevel, strong for screwing into (I tested it).
I bought (1) 12' board, ripped in half for the big top/bottom pieces, and (1) 6' board, ripped in half, for the RH/LS sides. They came in at 2 1/2 wide.
Below is my test of the bevel and 45deg miter, ready for cutting the real ones.
Workshop above the 3 car garage, COLD! (not heated yet), but big/open workspace. Lots of white powder/dust instead of sawdust.