When riding with one or more people I've had a problem staying close to people in front of me, not because they're going too fast but because I never feel very comfortable getting any closer than 2-3 feet away. I also have the same problem riding in double lines: I have problems staying close to someone else. None of this seems to be an issue when I'm riding solo: I can maintain a constant speed and stay laterally within a few inches of where I'd like to be, but in groups I can't bring my formations in any tighter. Any suggestions?