rs008f,
With cartoons specifically, you can filter heavily, sharpen a bit, and get more compression! My Script is not the best in this case. Since I don't do cartoons, I can't help you, but look around here and at doom9 forum (forum.doom9.org) for scripts specifically for cartoons!
You can also lower the resolution to 352x480 or 352x240 and get even more footage. Make some tests! I suggest you use lanczos resize, do a small sample and see how it looks on TV. The problem here is that you're dealing with full screen footage, which of course is harder to compress than widescreen stuff (the black bars take near no space)
[]'s
Vmesquita