Hello vovven47,
If there is no way to reach Rene Stambke to get a permission approved by him, the only way left is: just do it! -- Because, if Rene Stambke does not want it, he or an authorized person will already get in touch.
By the way, some time ago I had received permission from him to convert his tender to a snowplug.
This snowplow is now exiting on my plate....
MfG
hadotwe