Why in the world would you need a multi leg options position if you're so good at predicting short term moves in the underlying? What a waste it is to cross three markets to put on a position if you're looking to capitalize on short term moves which you say you can predict. Why not just use the futures? or straight puts and calls to leverage your directional speculation?
Trade smaller size and use stops in the underlying. Sounds like you're trying to drive a finishing nail with a sledge hammer by using an options position where you cross 3 markets in order to leverage a short term spec in the market
I don't understand.. how can I trade smaller than 1 contract? Am I better off waiting to closer to expiration before I get my panties in a bunch?
Butterfly is a rather complex position for such a simple goal. If you are looking for low slippage, you may consider looking elsewhere -- spreads or calendar.