There is quite a lot of dimpling to be done on the steel firewall panels to accept the firewall angles. Of course, these angles have to be countersunk to accept the dimples. I got a bit carried with priming and forgot that I hadn’t countersunk the angles. No harm done, I will just give the countersunk holes a quick coat of primer.
There are instructions to only countersink where there is a corresponding dimple. I couldn’t see where this should happen until I realised it only occurs on the diagonal angles. It took me too long to figure this out!