I have 2 Sandisk 4GB Memory Sticks, but both are completely full of Playstation Network games I've been buying up, I'd like to get a new card where I could throw all the games on one card and have room to add lots more.

Is 32GB currently the max size for Pro Duo?

I've also seen "adapter" memory sticks, where a smaller memory card is adapted to fit in another, do these work well with PSP?