Well, since I had no idea that the parts needed modification, about half an hour including the time it took to figure out how to do it. Sawing away the unneeded parts then took max 5 mins, the jigsaw went through the plastic like a knife through butter. I recommend protecting the leather during this process, since the jigsaw might touch it accidently, and it's easily damaged. The most complicated part was fitting #10. Since this part is very wide in the rear end and easily collides with the cup holders' rear end, I had to fiddle a bit to get back in. But no big deal.

If someone posts a picture of the "raw" knee pad part(s), I can show you what parts exactly I cut off.

/Thomas