531 and 753 tubing...if built correctly... ought to be strong enough to withstand some 'roughish' treatment, obviously if you go bouncing up kerbs or are on the heavy side...say 15 stone or more, then naturally you would be imposing more stresses to the tubing....and might need to consider a heavier guage tubeset.

I'm six foot and 12 1/2 stone and don't have any 'fears' about the tubing failing due to my weight.

Columbus Nemo [now discontinued] was a very light tubeset which had a size limit of 55cm if I remember correctly.
cheers Kevin