Benton, LOL yes you do. No wonder you are making good bows..
Riser block 12 inches long by 1 3/4 wide to start.
Mark the center at 6.5", measure up and down from that center line 2 inches. That will be your 4"grip area. But see below.
I lay out the actual bow shape on my boo and cut that out. I have a pattern already cut to shape and I just use that.
But from the center of the length of the boo, I measure up 2 inches, that is the top of the grip and also is the arrow shelf. From that line I measure up 2 more inches, that is the flare, and measure up 2 more inches and that's the end of the riser.
Then repeat that measuring down from the center. The first 2 inch line is the bottom of the grip area, second 2 inch line is bottom flare and the last 2 inches is the end of the riser.
I use 13 inch risers too, I just add an extra half inch onto the distance between the flare and end of riser on each end.