something in your original post doesn't add up for me.
I thought rail fence was square yet your block is 4.75 x 5.75 They are not going to match up I agree with the other post - not sure what you want to do here. Make it easy on your self and drop the fractions and use even sizes strips with your 1/2" seam allowances. From your original post it sounds like your blocks may be 10" finished but can't really tell with the limited information.