The idea is quite good. In addition, the availability of other devices may well be given.
So I'll give you reasons of fairness 3 star.
But:
1. adjustability: The metal lever also serves as locking screw - but could be moved only by forceps initially.
2. The weight of the metal lever, the zoom ring adjusts the camcorder easily on their own. So used in any way. This (D) ef (f) ect also appeared in 300 at the telephoto Pentax - albeit not as strong. Nevertheless, useless here.
EVT. could ensure the availability of a suitable plastic, a redesign of the lever.
As it is, it does not work but unfortunately: - //