You can place it for the highest you're willing to pay, even if that amount seems to be higher than your Gap-Up prediction. The order SHOULD fill at the best ASK showing, or near it. I say SHOULD because if you place a large enough order, the market makers might start playing games.
For example:
You think it might gap-up huge, so you put in a BUY LIMIT order for 100,000 @ .01 and the issue opens at .007. With enough volume, you SHOULD be able to get it filled at or near .007
Now, on the other hand, if you're a Whale and you put in an order for 20 Million @ .01, the market will probably detect that and gap right up to YOUR order, thereby making YOU the party responsible for that gap!
Good Luck