Scrap 5/8" particle board was ripped into 1 3/4" strips with 3/4" notches set 24" apart to hold tubing for bottom of fuselage (fuselage is built upside down on table).
Here you can see how the hold down block will be used with the cross strip to hold the tubing on the centerline. 
Bottom and top tubing tacked in place. Squares in place to check trueness. Welding rod diagonals tacked in to help hold position while the fuselage sides are bent in fore and aft of the cockpit area.
Doesn't seem fair to just show straight fuselage sides and then show a picture of the sides bent in. I was rather intimidated to do the task. Seemed like a lot could go wrong but it went rather smoothly. Just heat up the longerons just behind the cockpit area and carefully bend to the lines on the table to meet the tailpost.