Here some pictures and a drawing of the Fritz's Motor Box
The first 6 layers have a cutout for the throttle linkage.
This is a regular ball link - low and full throttle with and without the motor box - please look closely and you see the cutout. It is maybe confusing the other end of the box has a different shape - but this was the nearest solution to keep the strength to the maximum.
Sorry for the mix up.
Even Fritz took a second look...[8D]