The only feeder that I have ever seen having problems with comb damage is that one with the green plastic lid and feed tray. There are several negative reviews on
Amazon with pictures of bloody heads. Never heard of a grandpa feeder having any problems with that. Some of those plastic bucket and plumbing elbow feeders have had a few posts made with that issue, hens seem to be fine using those feeders although they aren't rat proof.
The Rat Proof Feeder can be used outdoors. Our videos are mostly two years or older feeders, long before we added an exterior modified feeder. And most were outside under no cover, not something that I recommended but they seemed to do fine except heavy rain. Some of the large commercial free range flocks that use our feeders have them mounted on pallets with zero cover, but those feeders get emptied every day as they can have 100 birds or more per feeder.
If you have an older model Rat Proof Feeder, just bend that lower front lip back about a half inch so the water doesn't run down and drip into the feed. Our exterior version has that done and a 1/4" hex nut used as a spacer with a screw through it so it can't be bent or pushed back. The lid over hand doesn't really matter as long as it is a 1/4" overhang or more. Rain will run under about that much, bead up, and gravity pulls it down.
Be sure that what ever style you buy to have it fastened down solidly with the treadle bottoming out on the ground. Remove all other feed including free range, adjust the spring if it has one to pre load the door, and follow the instructions. 100% of the time when a customer emails asking for help it is because they don't follow the instructions. In our case, the instructions have been the result of seven years of selling feeders and feed back from BYC.com and the customers. Go with them instead of trying to reinvent the wheel!
