Nice affects I like it.
To mask this off I would start with some general masking tape (the brown stuff or whatever tape you typically use). I start in the corners with a piece about 1" (2cm) and I mask each corner on the inside. Then I move to the middle overlapping the corner tape.
This leaves a 'ring' of tape with the sticky side out. The only 'stuck' area will the edge of the just above the grab handles are (that will be tricky to mask around with this technique).
Then I make a dome of paper using the part of the tape.
Here's a picture from the back
