For all the european players here like me who don't have access to darkstar 9 :
I used some grey ALR fabric from these guys : https://leinwandbau.info/en/projection-screen-fabric/high-contrast-screen-material-ambient-light-rejecting-alr-projector-screen-material/51/high-contrast-screen-material-ambient-light-rejecting-alr-projector-screen-material-1-1?number=LWB10051&c=21
You can order a roll of 80*80, should be more than enough to cover everything and you can do the ramps in one piece too.
Here are some photos with some fabric badly glued to a piece of cardboard for testing purposes :