RC Car Body Post Markers

I did it again - I painted the body shell and forgot to mark (or make) the holes for the body posts. Then I had to lend some (pretty cool) body post markers from Manni. This worked out quite right, but he wanted them back...
Buying something simple like that seemed wrong. Especially for 20€. So I bought some 6x3x3 neodymium magnets at ebay (20 pcs for 8€ incl. P&P) instead and designed my own markers.