Hi to you all.To Beedee in particular.The notion of Mega Sprocket is a very subjective one.I assume you are talking Off Road and or, possibly Hybrid,also standard Crank Arm length(170mm,give or take 2.5mm).I have two bikes,a 2000/2001 Bianchi Gold Race 600(Road Bike)& a 2009 Claud Butler Levante,Flat Bar Hybrid Road Bike,both on revised front rings(triple in both cases),and each on 140mm cranks(total replacement left knee necessitated the change),I am of very short stature(23.5" inside leg)and the restricted knee bend and short limbs became an issue.The spread on the Bianch is from 106 down to 28.54 using 52:42:28 with a 13:14:15:16:17:19:21:23:26 & 700cx23 rolling gear,the original was a 52:42:30 with the 13:14:15:!6:17;!9:21:23:26.The Claud Butler spread is 110 down to 22.97 using 46:40:26(the 110 very rarely used)with an 11:13:15:17:19:23:26:30 & 700cx23 rolling gear;the original was a 12:13:15:17:19:21:23:26 with a 52:42:30.The point of the options of my changes being that you don't need to go to a change as extreme as a Mega(34) final low and risking a bucket full of shift problems with the extremes of high to low and the demands on the cables and the possible need for a rear mech change,to a long cage type.One last consideration,my reduced crank length is the equivalent of a two tooth increase in chain ring sizes,or approx' 20% greater effort to turn the pedals(less leverage length).The moral of this story,short arse riders with replacement metal knees have hidden hurdles,don't laugh as you pass;their day will come.Happy & Safe Riding to You All.