I had the bung but then i found a better option.
Anyone remember the old classic mini wiper grommets?
Stainless steel ones with the wingnut on the back?
I bought 2 for £6 and have one in place whilst i prime and colour code the other one, works an absolute treat and is very flush
think itl be hardly noticeable when its colour coded and there'll be no pushing it through.
Will get a pic on, some of these seem to be thicker than others but i managed to get really slim ones. when ive done mine, if anyone wants the spare one they can have it free, i'll even stick a coat of primer on itT: