I have used a small Grandpa feeder for a small flock. The plate on that would not work with a crow's weight on it. We followed the instructions for getting our hens used to it over a period, and that all worked brilliantly.
Crows being so very intelligent, whatever system you go for would need a bin closure they physically can't undo, not even using tools. Or, get one they will work out and be able to undo, video them doing that, put that on YouTube and use the income stream to pay for the extra corn for them
Both highlighted statements are true , even more so when two crows stand on the treadle and are able to access the feed, as they like doing here.
Two crows on the treadle... that's my thinking, so I have so far not invested in a treadle feeder. My chickens get whatever they clear up in the morning, and then some grain in the afternoon. Yes the crows do get some, but not serious amounts, and I do believe that crows have a place in the eco system as well.
I am amazed how observant they are - as soon as the veg peelings etc get emptied onto the compost heap a crow comes to inspect it... so they must be watching from the neighbours' trees all the time.
Not sure how it will all pan out once we get magpies moving onto the holding, I have recently spotted some half a mile away, never seen any before this far out of town.