Interesting one when you first look at it, very interesting one when you painted it!
Budget canvas 16"x20" was used and a lot of micro tape. Measuring was quite a hassle but manageable. For the big triangle, you just take 2/3 of width and heigth. For the smaller rectangle, use 1/2 of the heigth and 2/5 for the width. That comes closest to what Bob did.
Lots of brush cleaning to do here yet fairly easy painting in all since it was finished in 105 minutes.