I made my drop pods in a similar way. I used a cd as a base and glued an empty margarine tub on top (the 1# size). They turn out just big enough for dreads and plenty big enough for a squad of marines or termies. The cds and plastice tubs were easy to paint as well. A quick blast of black primer (I run BT) looks good. It is covers well and looks dull like you would expect of a pod that just got a blast of friction heat on descent from orbit. Sometimes styrofoam need a coating of white glue (or Mod Podge) to get the paint to stick without running.