I went for a bike fit yesterday morning and from the measurements that came back it all depends on what style of riding you are going for, I ride a cyclocross bike so got my results for off road cyclocross and also road racing comfort, the fitting system used was through bikefitting.com. The results for cyclocross suggested a drop of 77mm whilst the road racing comfort suggested a drop of 24mm but this takes into account of your specific measurements i.e. inseam, torso length, arm length shoe size etc and alsogives the optimum fram size for your particular body sizing. Cost me £40 for my bike fit and took approx an hour with quite a bit of fettling with my bike as its not the recomended size for my body, when it comes to buying my next bike will defo take these measurements into account