BLV MGN Cube - improved front panel look

This is a minor visual change to the stock BLV Cube frontpanel. It changes the radii on the middle part of the panels to make it a bit more visually pleasing. As always this is a drop-in replacement. So just print all regular parts for the BLV MGN cube and just replace this part of the front panel.

Please report back if this part causes any issues for you, thank you! :)