Saving Old Seagulls

I have one of the plastic tanks on a late model EFNR. It originally came with one of the cheap plastic fuel taps, which is broken like many others by now.

I have tried two different replacement taps (traditional ewarts brass and an aftermarket plastic one) but they do not fit as there is a small restriction immediately above the brass threads in the fuel tank. The restriction is part of the molded plastic tank and about 1mm narrower in diameter than the brass threads below it. This stops the taps from going in fully/properly.

My question is, can I safely remove a bit of the restriction so that the taps screw in properly? I don’t see why not, doesn’t seem structurally important, but wanted to check if others have crossed this bridge before I do something irreversible. I think I have the same issue on another plastic tank but will have to check that later.

Thanks!

That restriction is to hold the brass threaded insert in place!

Why not try a couple of fibre washers on the tap threads, & don't over tighten, damage that insert & it will leak & you have a throw away tank