Watched the video, I think a 240 GpA rear spoiler / wing looks much better than that creation. But I respect the amount of metal working effort put in.
Fibreglass / carbon fibre is the go these days.
Your question was about side skirts though. Not the usual area for tweaks in a Volvo. However, whats fabricated needs to clear the jacking points.
Would you be making up something yourself with available tools?