You won't have any difficulty hitting the plates using open sights, so maybe choose a very heavy pellet and knock them down using the 'kinetic kill-zone trip effect' like the fellas with the .25s. But that is sort of cheating.

If the face-plates were painted white and the kill-zones painted black and the targets placed in well-lit positions on a bright day, you should turn in a very respectable score. The problem is that the kill-zones are often not distinguisable from the face-plates in the usual HFT conditions, I have had problems seeing them with a 6x scope sometimes.

Therefore, if it is within the rules, I think you should take some binoculars and 'spot' the targets before taking aim. Then at least you will be firing at the right mark.

All the best of luck!