Hi gents. The best way is to use stoppers behind the board, the issue with an extreme short throw projector is that the image will adjust dramatically if you tighten a screw or if the wall isn't entirely level that it is being mounted on.
If the curve is a happy smile at the bottom, put a stopper in the middle of the board and it will level the image then push projector back to fill out image and keystone.
If the curve is a sad face put stoppers on the 2 corners of the board.
I find the rubber from the wall mount brackets (included in board) to be very handy stoppers.
I hope this helps.
Paul.