Well, I can confirm this works for me and me only. Someone else please try this to see if this works for others. Here's what I did.
My save was in the 8 MB range. I saved my game in a town, restarted my PS3, loaded up that last save, went into any small interior (I used "Jorgen and Lami's House"), and saved my game. Instant 80-120kb. I did this quite a few times and my save went from 8322 KB to 7663 KB. Pretty happy this at least works for me, but it's also a pain in the ass and takes a while. I also don't start any new quests and only complete the ones I have open. Starting new quests, as well as adding new items to my inventory only bloats my save. My fps still dips like crazy in some areas, but if I get the file size down as much as possible and see a major improvement, I'll let you know!
This has become a game of "keep the save file size down and only explore" rather than experience "Elder Scrolls V: Skyrim"

