Since you have a basket, I would consider putting a mount on the basket and getting a 2 foot long firestik. If you decide to keep to your door jamb choice, pick a 4 foot firestik so that the tip of the antenna is 1-2 feet over the roof. Either way, they'll do fine for trail use. If you ever want to go for distance, you want the longest antenna above the roof line (in general).