I LEJoG'D on a Giant SCR1.5 , I've not checked the spec of the Defy but I think the spec will be some what similar. the bikeoriginaly had Shimano Tiagra group set, but the hubs were as others have pointed out a compromise ie cheapo, earlier on this year I built a new set of wheels and used Tiagra hubs to complete the set up, and as soon as I hit the road (not literaly) I could feel the diference. that aside, it was the only change from it's original spec apart from new tyres and a Brooks B17
I've got a pannier rack on, as I need to carry my gear for work each day. I've been touring on the bike before and after the LEJOG with both panniers and no problems
This was taken on my first 100+ miler from home to Barmouth Sept 2008
I've swopped the panniers for a couple of smaller Halfords ones (the smaller the pannier the less weight you can carry)
I'm happy with what I've got and wouldn't change anything at the moment. The bike was recomended to me by my LBS as it would fit the criteria that I specified.
hope all that helps
Percussive maintainance, if it don't fit, hit it with the hammer.