As I am researching this, I found a lumber company that specializes in Spruce for aircraft and boats. Mc Cormick Lumber in Madison Wisconsin. Spruce is 16 and 20 foot lengths and comes in 4 quarters thickness. After I figure out what I need, it comes to 1/2 price. Of course, I have to pick it up (50 miles) and process it (I do have a saw and planner) so I think I will go that route. The caps are the most important, the ribs can be made of douglas fir which is local.