I know....three posts in one day is way too much. But did I say I am stoked? LOL
I have 19 of the black blocks made here. I think 20 will give me a nice lap sized quilt. EQ says that should be 57.5 inches wide. If I do 12 taht means indivicual 12 colors. The way an on-point quilt works is that you essentially count every other row on the vertical.
You also have to decide whether to end your row with a "up" or a "down" block. Either way, but I think if you ended with one of each it would look odd. So think about that when you make the decision on how many horizontal rows to set.