As in it would fall right through the soundhole? What guitar brand and model are you using?
An off-the-top-of-my-head solution would be to fit it as close to the fingerboard as possible and tape the pickup to the underside of the guitar top.
Another solution is to have a Under Saddle Transducer pickup installed on your guitar. If I'm not wrong, the Transducer pickup is placed underneath the saddle and the wires go inside the guitar through the bridge and meets the endpin which serves both as a strap button and a quarter-inch jack. It's a permanent pickup system but with minimal drilling of holes.