I'm 6'1 and weigh about 150. I have an extended (non telescoping) steel seat-post which is about 1.5 inches from being fully extended. I mounted the rack as far down as possible, while still allowing the seat-post to retract and act as brakes while the bike is folded. When mounted the cross bag hangs about 7-8inches away from the seat-post. I was having to carry more things with me, passing the 25lbs weight limit of the rack. This was noticeably affecting my cornering speeds as the brompton felt unusually top heavy. But the main reason I switched was because i found another setup which lets me mount just about any backpack and have the brompton rear rack support all the weight. Also I hate shoulder type bags (messenger bags, crossbag etc.) and being able to mount a backpack convinced me to switch. I stole the idea from these guys