I have the HRC box on my 21, and it does not affect lights or anything else a roadworthy machine needs - you're getting confused with the 28!

On mine, I removed the 2 grey plugs from the HRC unit, and crimped on pins to mate with the NSR loom. I then installed the pins in the loom sockets, put masking tape round the whole joint to create a bath, and filled the thing up with silicon sealer.

This is a recognised aircraft 'Battle Damage Repair' technique, and has lasted for two years of racing without a single mishap.

Should I wish to remove it, the whole lot will clean up and the original loom will plug back into the PGM.