You can get a pretty good score with Fox, just hammer B to fire his Blaster as fast as you can, and leave just enough time for a good Smash.
I got a good score with Roy too, skip picking up the bat, Smash up a few times, and leave enough time to fully charge his blade by holding B. Ideally, hit the bag as it's falling. Roy should take 10% damage and the explosion will send Sandbag really far, I got about 1300 feet.
Yoshi's strategy of lots of downward kicking works for Jigglypuff too, I've got about 1200 feet with her.
And I got around 1300 with Ganondorf, I forget how...I think it was lots of upward Smashing and a right Smash as the bag was falling...Just be careful to time his Smashes so that the bag goes up and not forward. Good luck!
"Like the moon over
the day, my genius and brawn
are lost on these fools."
-Bowser, SMRPG
Sometimes I dream about being carried off by a giant squirrel...Does that make me a nut?