Wait a minute.

Maybe it makes more sense to NOT add strips of dark prints to my smaller blocks, but instead  to use different sizes of black sashing to make up the difference.  Tonight I started to add a 1/2 inch strip to one of my blocks & it was such a tiny piece of fabric that it was hard to work with. 

I'll do some measuring and some math to see how much trouble it would be and then we can decide.