We've rented a few slingshots and I have a flash drive I take with to listen to music. Up until this past week, we couldn't hear the music when we got over 35 mph. This weekend, the volume was fantastic, I was on interstate and I could hear the music just fine. They have all been R models, anywhere from 3 years old to new.(The one we could hear was about 1 year old). Is there setting on the radio that could make the radio more audible? I didn't play with any settings/buttons.