The roll bar attaches to the fuselage with a Frankenstein bracket on each side. Two pieces of angle join together, get bolted to the fuselage, then bolt to the roll bar itself. I didn't get pictures of the process it took to just get the angles to the point below. I clamped the smaller angle inside the roll bar, the larger angle to the outside of the roll bar, then held my tongue just right to line them up, clamp them together and drill two holes in the bases for "keeper" rivets. The rivets are just there to make later assembly and drilling easier.
A few of the steps in attaching the roll bar structure require lining up pieces with the skin, so I put the top skin back on.
The roll bar is linked to the rear baggage bulkhead by a big U channel brace. The aft portion has a 1/8" thick piece that stiffens up where it is riveted to the top skin. I match drilled that, countersunk it and riveted it to the channel. I would normally just wait and prime everything before assembly, but since there are certain parts like this that need to be riveted on before fitting, it's faster to just brush some primer on mating surfaces and continue on for now.
The first trial fit of the roll bar and upper brace.
Next up was the tricky part - getting the attach brackets located in the right place for drilling to the fuselage. The instructions don't really provide any guidance on the best way to do this. The problem is that there is no way to clamp everything and drill the holes through the brackets while it's clamped together. The front surface of the roll bar needs to match up with the front edge of the skin. However, the brackets are not the same width as the roll bar, so you can't just remove the roll bar and match the brackets up with the skin. I used a straight edge set across the fuselage to line the front of the roll bar up with the skin on each side. With that where I wanted it, I carefully clamped each bracket in place (centered on the roll bar outside surface). I had put tape onto the horizontal fuselage surface, so then just traced the location of the bracket. That's never ideal since lining a part up on a line is never as accurate as drilling with all parts clamped together, but there was really no choice. The holes that attach the vertical legs of the brackets to the roll bar aren't drilled yet, so even if I am off a little in lining up on my taped line, there will be enough wiggle room when match drilling the vertical legs later.
I pulled the roll bar off so I had access to the brackets again and lined them up to my lines. The outside bracket does not follow the curve of the fuselage. It has to be filed to shape. I set the front corner just inside the skin line and clamped the bracket down. Little by little I drilled the mounting holes until I was up to the 1/4" bolt size.
I don't want to drill the attach brackets to the roll bar itself until I'm sure the roll bar is solid and located correctly. The best way to do that is to get the top brace in place (I had just clamped it to the roll bar before). I drilled the long piece of angle to the brace and then match drilled a smaller piece of angle for each side. That stiffens everything up considerably.
