The 5/16" x 5/8" strips are for the nose rib stringer. Nose ribs are notched for this, and the stringer is epoxied into the slot. I bought 14-foot lengths of spruce for my spars from ACS. You need to call them to get the longer lengths. It is OK to splice the spars as long as you do it correctly, and I recommend you do it at about 2-feet from the outer end.