My dads friend reshelled a nissan works cherry coupe and added the "original" speed holes to the shell and body again. It took him 2 weekends and he had a icecream container full of scrap at the end which weighed about 3kg. A lot of work for little gain. I would be concerned about adding speed holes to a car that didnt already have a cage and be seam welded.

Much easier for the driver to the gym haha.