Okay, once I painted it, it started to sag a little. Cool, I thought, looks good. I left it to dry, and when I came back, it was taut again. Damn, I thought, and tried to pull it down again while adding more paint.
And then it broke.
It is relatively easy to fix broken UHU, I discovered, but it is a bit annoying since it means adding more and more UHU. So I finished it up, and this is where I leave it:
View attachment 43174
(I'll look into making a sagging effect and using plastic at a later date, thanks for the input everyone)