My husband and I just purchased two Giant LaFree +1 bikes. We bought 33" folding locks, but decided we should get a U Lock. We'll probably keep the folding locks to use on the front of the bike. We plan to ride in many different types of places -- trails, towns and possibly cities. I know the U Lock is supposed to have a tight fit, but I was wondering if anyone could recommend the best size. Two locks we're currently looking at are (1) Kryptonite NY Std Heavy Duty U Lock (8" inch interior length) and (2) Kryptonite NY Fahgettaboutit Mini U Lock (6" interior length). Does anyone have any suggestions?