I bought two 14-foot spruce spar stock pieces 3/4" x 5" from ACS and cut all my spar caps, compression struts, and diagonals from them. I still have a few strips 1/4" x 3/4" left over. Even using a thin blade on my table saw, I lost 1/8" of wood with each cut. I still saved some money over letting ACS cut everything, BUT shipping was not an issue since I only live 30 miles from them. If you make proper scarf joints, they should be every bit as strong as a solid piece. I plan to splice my TE using a 15 to 1 scarf. If I were in your position, I would go with whatever sizes of wood gave me the best price, shipping included, but would order lengths that only required one scarf/splice per spar cap.