Filling holes in sheet metal around penetrations?

I don?t (yet) have an RV but in tracking down cold air drafts in my plane I have found areas where fuel lines (at the fitting) pass through the fuselage behind the wing fairing. I would like to fill the holes but since a fitting is there I don?t think RTV is appropriate. The gap is also quite large (1.5? hole with 1/2? or 3/4? fitting in the middle).

Any thoughts on what I should use for this application?

Thx.

What I do.

Find large area rubber grommets, cut to slip over fuel lines and seal in place with RTV or make from dense foam rubber disc with slot cut like a grommet . I have done both methods many times. The foam is cheap, easy and with practice will look very tidy and light.

If the fitting is indeed ?in the middle?, that is not good practice. The line should extend beyond the hole with the fitting on one side or another.
I like the foam plug idea but it will need to be easily removable so you can inspect the fitting. It might not be a bad idea to use a light colored foam so you can see a leaky fitting easily.