Ok: I know you probably don't want to hear this but I would remove the border and increase the strip by .25 inch on each side, this would give you your 36.5 inches which would make the blocks divisable by three and multiples of 3. Mamahen: What a shame you want to add a border since the 6.5 inch block would fit perfectly with your current measurement. If you want to keep the 6.5 inch block your going to have to add 3 inches finished on each side, or 3.5 inch strips. This will give you a measurement of 48.5 by 48.5 which will allow you to use a 6 inch finished block. Two sides will have 8 blocks and two sides will have 10 blocks. I hope no one minds by over participation here, I just happen to be on the computer and hoped to help.