Printing it now. Can hopefully test it later because tomorrow I am leaving on a class trip. 
/edit: Print is done, I also printed another lower part so I can just swap them depending on the endmill. What I can already say: They can’t be longer than 32mm. If I bend them inside, they roughly leave 5mm of space around them (they are not going to bend that far on the CNC, but any longer and they might).
/edit: Perfect length, does not get sucked in neither by the router nor the vacuum, though I did not test it when it goes below 0. The dust shoe on the LR3 sucked it in all the time.
That’s when it runs at 24 000 RPM and the vacuum. Slight bend, that’s about it.