Summary

The suggested mounting method for the electronics board of the Velleman K8200 is both unstable and risky. The board is mounted with two screws through the edge of the board. If the board case it hit by something it is likely that the PCB will break clean off, which would be catastrophic.
I have constructed a mount that solves the problem. The mount is bolted to the printer frame using the usual method of square nuts and M5 bolts. The electronics board is then fastened to the mount using four M3 bolts. The result is a safe and reliable installation of the electronics board.
I divided the mount into two parts to make it easy to print; a mounting plate and a rail. The rail fits between the plate and the aluminium frame to provide stability. It is not necessary to glue the parts together since they are held together by the M5 mounting bolts.
The long m3 bolts in the picture are 25 mm. I did not have anything more fitting available when I test fitted the board. 15 mm would have been perfect.

The mounting plate has to be printed on a rather high infill to be stable enough. I recommend something like 70-75% infill.