[pathetic excuse]I reckon it's more difficult when you weigh 14 stone[/pathetic excuse]
I think it's a reasonable excuse, but it probably depends how much of that 14 stone is lard! :P
I'm no stronger at 12.5 stone than I was at 10.5, so I reckon that extra 2 stone of blubber must severely hamper my ability to do body-weight-based exercises. My brother can do chin-ups and I can't, although I think I'm still a bit stronger than him.... but I'm a full sack of potatoes heavier! :lol:
The fact that you're tall probably makes a difference - long levers vs. short levers must come into it somewhere.