There are many people using rubber maid tubs as raise up enclosures, just build more on to it and put 2x4s on the sides to stop it from warping. How big is the savannah?
Depending on size it may have any where from 2-6 months until you will have to move it to a new enclosure. That gives you some time to build an adult cage but remember when properly maintained they will get 3/4th there adult size in the first year. Another thing to look into are metal troughs as they come in a variety of sizes and can hold substrate with no problem, again all you will have to due is build a top section of the enclosure made of wood on top.


Bryan