I'm really trying to use up my batik scraps, so am thinking of doing a black border, then a narrow border of the stripe, then a row of 9 patch blocks using black/batik (it will copy the 9 patch formed between the main blocks) then another stripe and then black. That should also get the final size bigger.
I think I may go with a narrow neutral border, then piano keys for the smaller, light one. I've got piles of 2.5" strips already cut.