I use plywood cut to size for the dog crates at the rescue as I pinched the trays to use at home. I always put two shelves in my crates so guineas can have the top. There is still enough head height left for a rabbit underneath as they are so tall. I put newspaper topped with hay on the shelves and it works well, although some more peices cut to fit the sides would help with the stray hay and poo :? I keep meaning to add those, but as they are sitting inside pens with their own bedding it isn't as important as it would be in a house.