thesamba isn't
always authoritative. Ferinstance, I asked Everett Barnes about interest in front wheel skirts and he thought the idea would get shouted down.
The gap between the fenderwell and tire is narrow and full of churn. No guarantee of a positive pressure gradient to the underside. If you cut the vent[s], you could do A-B-A testing.
I liked the solution Harry Bradley suggested in his drawings from the '80s. I know I scanned it but I haven't found it in my albums. Basically he added a 1.5-2" C-bracket on each mounting bolt to hold the stock fender out and then covered the gap with perforated metal mesh. He also had the taillights and turn signals in there as well.
I'll keep looking through my backups.
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The roof-top light and whatever is going on under the [raised] front bumper made me think 'rural fire department'.
https://www.google.com/search?q=battle+car+beetle