Thats why you use velcro or magnets so it can easily be removed. Instead of trim you could use pvc so it doesn't get saturated.
Morter tubs are great for rats but I think that they are a little to big for ASF's. (IMO) I really like the bus tubs and havent had any problems with chewing. As long as you make it a snug fit against the hardware cloth, you should be just fine.