Hugh,
In regards to what to use to keep your small foods from falling through the cracks of the screens, I have an answer that may or may not be safe, but I’ve have years of good luck. I put tin foil on the screen, then put a spritz of Pam cooking spray, then use a bit of paper towel to make sure the foil gets covered. I don’t spray the foil completely because I don’t care for the oily texture that remains after dehydration. When I use foil, I only use every other tray giving my machine ample air flow. When my process is done, my project slides off and into a Ball or Mason jar where I air seal it. Examples of food I use this on is corn, peas, scrambled eggs, cabbage, et cetera, whatever I’m slicing and dicing small or is rather soft. Out of all my canning and prepping items I have purchased and obtained over the years, my dehydrator was my most expensive. It is my favorite gadget though. I use it the most. My family never has a clue that I’m cooking with dehydrated food, and I enjoy the wonderful aromas my house has when my machine is running. If you don’t have a dehydrator in your kitchen tool kit, treat yourself. Dehydrate some banana slices sprinkled with cinnamon. Oh my! Time is short. Get your machine going while the fall harvest season approaches and there is abundance. Put up all you are able. Your machine needs to run 24/7 right now. Blessings. – J.