Originally posted by Danjb
Well there is that option, but obviously a fix would be preferable.
Ok, a fix... try using Map16 tiles for the center part of the mushroom, and for the ends (Where Mario Falls), edit the tiles so that they act like tile 106 (106 - only the top of the tile is solid).
Then save your changes, and add the newly edited edge pieces. If they don't work, then you can resort to making act like 130.