Fat chance of a 5mm gap with those guards on the Defy.
I have them and the clearances were extremely tight with the 25c tyres that came with the bike, but they fitted and worked well, quite a bugger to adjust though.
When the tyres were replaced with 23c's then clearance was a lot better and they were far easier to put on and adjust accordingly.
Fitting them, especially on the rear is most easy with the bike suspended correct way up and the wheels and brake calipers need to be removed. Start by attaching at the brak caliper, then attach to the rubber grommit on the back of the seat tube but do not over tighten. The rest is easy
Pics of mine with stock tyres are
http://www.cyclechat.net/threads/my-return-to-road-bikes.61710/#post-1157051