And now for something completely different... gap filling

 Time to switch to something else. The rear of the car has a gap between the chassis and the bodywork;

This is dealt with by a GRP panel on the MK HSR, that is just visible in this picture;

But while my body kit did come with that infill panel, it's nowhere near long enough! Which is really odd, because I don't remember cutting that back edge so it's not as if I've made it not fit.

Anyhow, there's a few things to consider for this;

1. It will be made out of aluminium. It needs to match the rest of the interior so aluminium makes sense. I also have a sheet available. 
2. It needs to fix to the body and the chassis. It might sound obvious, but for more strength on the body across the back it needs to be fixed.
3. It needs to be removable. Along with 2 above, the fixings need to be removable. So rivnuts or clips. 
4. A curve would be nice. As the body is horizontal and the chassis is (near) vertical a gentle curve would look good. However it does add to the complexity quite a lot. 
5. It needs to be trimmed round the roll bar. Not a major problem, but again another very visible trim that needs to work well, no room to escape. 

Some pics for reference;

These two corners could cause me some issue. The panel needs to line up with the small tab I left from the side panel, and also sit well with the edge of the body for it to look tidy. Then a cutout for the rollbar before the long run. 

You can also see in these pictures where the top plate for the suspension mounting is higher than the cross bar. That's another gap I need to infill somehow.

First off I think I'm going to make a wooden pattern. Cutting and forming the panel is not going to be easy so I want to ensure I get as close as possible with a pattern before committing to anything. It'll also let me figure out how much of the GRP I want to cut out of the corners, I doubt very much that it will stay as it is because it just doesn't work. I cut it like that so the roll bar could just slot in but it's not giving me any benefit.

One more pic for reference, this is how high the gap is (70mm). It also shows where the metalwork has to get to. That pic does make me wonder though, a right angle rather than a curve might work better with the body. Having it come directly up and then across means that I have enough GRP to trim back and make it look flush. I was going to use U trim on the GRP in that corner anyway. 

And one last check before I start, I am 99% sure that horizontal part of the body is a straight line but I ought to double check it. Even if there is a slight curve I think I'd prefer it to be flattened out. 

Let the panel forming commence...