Thanks Annette - I didn't see your comment until after I worked on the feeder. Silicone is about as inert as can be, once its cured. I think the bees won't mind. I'll let it cure for 3-4 days before pitting it on the hive.
If, once a year, the pressure washer won't destruct out the bee carcasses from under the screen, then I can remove the 3 screws along the top, and remove the screen completely. The silicone will peel off the plastic pretty well. Then after its cleaned up, I can put the screen back with duct tape and the screws.