Polycro Groundsheet corner tie-off technique

Hi all! Love this sub but this is my first time posting a question. I got a polycro groundsheet from Gossamer Gear. It's just about the perfect size (with a trim on one end) to be a good groundsheet for inside an X-Mid 1P (since Durston is out of his sheets and who knows when they will be restocked).

Here's what I'm wondering. Has anyone come up with an ingenious corner tie-off solution for this material? I'm thinking of folding the corner back on itself once, sandwiching a nylon or rubber washer inside this corner fold, then gluing it all down flat with epoxy or silicone or something. Once it's dried/cured, punching out the polycro material in the hole in the center of the washer: sort of making a DIY grommet. Then shock cord threaded thru, with hooks to attach to stakes at the fly stake points.

I'd love to hear other ideas or see anything anyone else might have done. If I do this method I will definitely post it here!

ETA a little clarification: I'm making the groundsheet to fill the entire square footprint of the X-Mid, not just the parallelogram inner footprint. This would give the vestibules a clean/dry floor for gear as well. My only concern is that the trekking pole handles will wear on the groundsheet so I'm also considering reinforcing those areas with some circle material samples I have from RSBTR (just gluing them down with contact cement) - may or may not do this lol

Thanks all