I worked with Henry at flexvat.com to create a custom vat for Draken I users. He said it should be available soon, but if you are interested now, please let him know!
The vat was designed around the original acrylic vat provided with the Draken I printer, so it fits properly into the vat holder frame.
There is an acrylic support plate under the FEP, which is elevated and stretched. The vat is assembled using the multiple bolts and there is a gasket in between to prevent leaks.
I've used it for a while and have not yet needed to replace the film. The plastic of this prototype does absorb some of the color of the various resins I have tried with it. I asked Henry if this is normal and it said it shouldn't be a problem.
Cleanup is pretty simple using isopropyl alcohol and soft cloth/towels.
If you are looking for a true flexible vat solution, this may be the one you are looking for!