The roll bar has to be the right width and height once it's all assembled. I measured the fuselage width and subtracted the width of the two brackets that attach to the outside of the roll bar. This gives the width that the roll bar itself has to be. After a quick look and realizing that the parts were going to take quite a bit of manipulating to make them fit right, I decided setting up a jig would be time well spent. I translated that measurement to a board and screwed down pieces of angle to act as stops. I also attached blocks for the bottom portion, since aside from the width, the roll bar also has to be a specified height at the center. It took a lot of back and forth, but filing about 1/8" from the center joint and giving the bottom edges a slight angle did the job.
With the width and height sorted out, I clamped everything down to keep it all flat.
I match drilled the center splice plate.
There are no pre-drilled holes in any of these parts. The front and rear u channels get connected together with 1/16" thick lengths of aluminum that nest inside each flange. I ground the corners of the 1/16" piece so it would set better into the curve of the flange. I laid out the rivet spacing on lengths of tape, then put the tape on the flange (easier than marking the spacing out directly on the awkward curve of the roll bar). The strap (not really a strap I suppose, but easier to just call it that) tends to lift up as it's drilled. I clamped it in the center, drilled, clecoed, then moved the clamps and worked my way to the ends. I started by drilling at #40. Next I'll go back and upsize them to #30.
