Extended Baggage for PA-12

I bought a PA-12 last winter with the intention of rebuilding it in the next year or so. Turns out it's in much better shape than I thought it was so I'm planning on flying it for a few more years before the rebuild (lets me get into another project but don't tell my wife). Unfortunately, I'm a little short of room inside and always seem have trouble getting the last sleeping bag or engine cover in. Obviously an extended baggage will be part of the rebuild but anyone out there have any thoughts on a way to add a small extended baggage to the upper baggage area without too many modifications?

I would think a belly pod would be your best bet.

Tim

I thought about that but I'm a CFI and do some instruction from the back seat. An added benefit of an extended baggage would be to move/raise the headliner and give me enough headroom in the back that I can sit up straight.