Bicycle Mechanics - Adjusting finger device which secures chain from falling off front chainwh. to inside

Does somebody have experience with the above question or can quote an instruction in this regard?
The question is what height? At the height of the teeth or slightly above (so that it funnels the chain onto the teeth?) Also the question whether rather forward rotated on the down tube, so that it is at the highest level of the smaller chain wheel or rather slightly backward rotated, then it is at the level where the derailleur moves the chain (was equipped on a Scott CR1, and was originally set at the level below the teeth, which appears too low to me?).
I acknowledge all my fellows advice that perfect front derailleur adjustment comes first, but the device seems to makes very much sense in protecting the carbon frame in case it still happens and in racing where under rough and quick downshift actions the chain still has the tendency to fall inward once in a while.
Thanks :rolleyes:

Third Eye Chain watcher
Deda Dog Fan
N Gear Jump Stop

Functionally they are pretty identical. You have to get the right seat tube size for the Dog Fang and Jump Stop. The Chain Watcher expands enough to fit any common seat tube size.

I use both the Third Eye and the N-Gear on various bikes. I have the upper edges set above the chainring teeth (to act as a funnel as you noted) and the guide plate is set as close to the teeth as it can be while leaving enough room for the chain.