wow man ......... you are really into this thing. I like the repair to front end. Thats some great work.
From what I know, all the Beetles had the same paint finish (from factory) as the upper body. (See videos on the paint process at youtube.com). So I can't say what you should do about the under coat but my vote is to keep the fender wells have the same finish and gloss as the rest of car. (I personally hate the blacked out fenderwells. For Storm, sorry bro but thats how it is. I've see the Things in the Naran Intensive Care Project and they had the same finish in the fender wells as the upper body). Yes, I said same paint finish and gloss. I'll type it again ...... the fender wells should have the same finish and gloss. If you missed my last 3 sentenses, here is what I said ..... the fender wells should have the same finish and gloss as the rest of the upper body.
Not bragging here, but, I have an original car ..... it has the same finish and gloss as the rest of the body. See my profile pictures. (though those pictures don't show the fender wells).
Hope this helps and keep up the good work and keep the pictures coming.
MSK
P.S: The fender wells should have the same finish and gloss as the rest of the upper body.