After I put the stringers in, then I put the diagonal- cross pieces in. They are staggered so the top and bottoms cross opposite. I went ahead and built a pipe tunnel out of light 3/32 balsa in case I go with long tuned pipes. Marco Benincasa did this at the Tuscon Shoot Out last year and I was really impressed with his power setup. I heard that the long pipes make the idle a bit tempermental, but since there are no tailslides at the Don Lowe Masters, this should be no problem. I had to remove the center of bottom bulhead to make room for the pipe tunnel. Will put the rudder servo tray up higher to clear the pipe tunnel.