I finished fine tuning the epoxy sealing on the passenger side. After some more sanding, this is the result of how the plenum cover now fits the front baffle. I see no more air leaks in the corner.

Then moved my attention to the pilot side diffuser. Here there is still some work and it has a rather significant air leak gap near the left top in the image where the diffuser, cover and front baffle meet. I could have lowered the side arm of the front baffle a bit but that would decrease height and cooling volume more. Easier solution is to use some flox and close the gap with some extra epoxy.

Here you see the gap

I used plastic tape and some PVA119 loosening agent liquid plastic to mask the diffuser, plenum cover and front baffle side wall. Roughned the top surface of the diffuserand then poured some flox onto it.

 When pushing the cover on and thightning the screws, the flow poured out and with the rest, I filled up the remaining gap on the side wall.

After 1 day curing, I took it of and got this result. It looks a bit funky but it does the job and seals it of perfectly.

 Put it back in place. I'll need some sanding to smoothen it but overal a good job.

 No more airleak here.