I use fleece flippers in my Midwest cage - I like them. I bought a set from the store then made some extra covers for them. In all honesty, I like using my covers better, as I made them a little larger and they are easier to get on and off the coroplast! Plus you can get some really fun designs - I've bought loads of fleece to make up extra covers for different seasons! The pigs seem happy on fleece too. I expanded my Midwest cages, got them up onto low tables to make them stable and put a sheet of coro in the bottom to make cleaning easier and added a kitchen too where I use carefresh. I will say the girls are a lot tidier than the boys - the girls tend to keep their poops in the kitchen area - the boys poop everywhere lol!
I've certainly found it a lot easier to clean since I expanded and modified them, as most of the hay stays in the kitchen area. Getting it off the fleece can be a total pain and the canvas bottom makes it tricky to clean.