I made one that is for a twin.. well I'm still working on designing the borders, but I believe my blocks are 6" too. I didn't put any sashing between mine. Instead I put a 6" tone on tone block between each crumb block and put them all on angles. I think I had close to 80 blocks when that part of the quilt top was completed. Once you get started they become very addicted and alot of fun to make!!!!!!
Good luck with your quilt!