OK, your alternate block will be a fourpatch made with two solids and two small four patches, right? if so, the finished size of the small fourpatch is 5 inches. to make a fourpatch that finishes at 5 inches you need to start with strips (or squares) that measure 3 inches when cut...that dimension reduces to 2.5 inches after seams are finished....the solid square in the smaller fourpatch would be cut at 5.5 and finish at 5. Does that make sense?