I convinced them to stripe of 4 full parking spots, which is a total of 36 ft wide. And considering we only have about 7 people that ride (and they aren't all here at the same time) I think it's plenty of space. That's 30 ft for MY bike, and 6 ft for the rest of em.
I laid out a parking pad for motorcycles at my last job and here is what I came up with. It was design to handle 10 bikes at 5'/bike and 9' long. More than enough room. You could make each spot 6" narrower and still have plenty of room.