Got a few hours to work on the plane today. I temporarily fit the roll bar. 

Here you can see the bracket doesn’t fit one top of the flange. For the tip up canopy it needs to be trimmed. 

Here I’ve marked where I need to cut the metal. 

This is after I’ve removed the required material, I rough cut using my angle grinder and then filed it down to the line. I radiused the corner and then hit the whole thing with scotchbrite. It was a lot more difficult that I thought. 

I then spent some time fitting the seatback slots to the cross beam. 

I’ve clamped the angle bracket, to the brace here and used some #30 drill bits to get the 1/8th spacing required. 

Here’s another view of the angle after I’ve drilled it partially to the cross brace. 

I also marked out the holes for the canopy attach slots. These need to be modified for either slider or tip up, luckily it wasn’t too difficult. 

I then refit the roll bar to the fuse after fitting everything back together. I still need to adjust the height of the roll bar. 

Here’s the aft channel clamped. This will get drilled to the roll bar and riveted together.