Yes, nanna-up-north has the proportions correct. I would start out with an 8" block and then draw a grid of 1". Draw your grid-line on the surface you are going to paint using 1 foot grid-lines. Then draw you design on your painting surface referring to the 1" grid and make reference marks on your 1' painting surface. I did this quite often when painting scenery for the theater especial drops from designers sketches.