A number of us have been caught out by those pesky clamps, and a lot of tempers frayed!
It's quite fiddly, but this worked for me after much head scratching and a few breaks to calm down!
Don't try to fit the clamps with the tail pipes fitted...you'll cry!
1. Remove the tail pipes (this does require loosening off the right side header pipe).
2. Remove the 2 clamps.
3. Remove the graphite gaskets and the steel ring in which they're housed (I then replaced the gaskets for new ones, but is is a bit of a pig to separate them from the steel ring).
4. Pre-shape each gasket in turn by placing it over the pipe fitting on the cat that you've removed (with the steel ring facing outwards) and gently tap with a mallet (it's a relatively soft material).
5. Once pre-shaped, fit the graphite gaskets to the clamps with the steel ring facing outwards and the open (bolt end of the clamp) pointing to the front of the bike.
6. Spin the nut onto each clamp just enough to bite.
7. Slide the closed end of each clamp over the shoulder of the x-pipe then push the open end over the shoulder and it will click into place (it does take a bit of force). Note that the open end of the clamp (with the nut and bolt) must face forwards with nut facing downwards. If you still can't manage, re-shape the gaskets (step 4) but tap a little harder with the mallet.
8. Hold the clamp so that it doesn't slide off the shoulder of the x-pipe, then tighten the nut until the clamp will just spin on the shoulder of the x-pipe.
9. Refit the tail pipes - there is a steel pin welded onto each pipe that must slide between the open ends of the clamp. Check that the clamps are still over the shoulder of the x-pipe.
10. Tighten up the clamps ensuring that they remain sat on the shoulder of the x-pipe (which they should do if you've followed the instructions above).
11. Refit the remainder of the exhaust system, start the engine and test for leaks...when I did one of the tail pipes leaked because the sodding clamp had slipped off the shoulder, so I had to patiently repeat the whole process...and that was after I tried to refit the clamp with the tail pipe on
I think I've remembered everything.
Hope it helps.