People run a front aerospoke because they like how they look, they dont run a rear because sometimes the hub breaks loose when you apply the torque applied when you skip/skid/apply lots of back pressure.
If you want to keep up, it really doesnt matter though most people would suggest about 70 gear inches. I run a 44/17 and keep up when I ride with people on road bikes. I would try some different gearings and see what you feel good running. If you're worried about keeping up, you should be fine, you might just have to spin more or stand up and mash on the hills.