I would suggest sticking with glass for feeders and staying away from plastic. Especially if your location gets wide temperature swings. Plastic will tend to "pump" the syrup out with temperature swings.
This has been my experience as well Robo. Glass jars will do the same thing, but not to the same extent. I have found Boardman feeders Packed with dead bees to the point the syrup was dripping out the front even with a glass jar.. 60 degree night and 90 degree noon time temps.
I may well end up modifying the feed stands to accept the wide mouth jars, but would prefer to keep the small mouth as long as possible..
You can still order half gallon jars, but I will probably modify the stands before going that route. Each of my stands takes three 1 Gallon jars, and the bees will empty all three in about two days in early spring and late fall. When the jars "weep" during temp rises, the syrup drips on the stand board and the bees simply clean it up. So no real issues, other than feeding wasps.. However... rum and coke in hand, I enjoy sitting, watching the bees, and wield a stick of sufficient diameter that it does not flex when i smoosh a wasp. I find that each of those yellow jackets I smoosh provides me with a sense of satisfaction only to be found when destroying a critter trying to get into the Hen house.
So in your travels.. keep your eyes open for gallon jars with the smaller 2.5 inch lids and please let me know if any are spotted!!!