Hi Terry,
here's the aussie website I'm not sure about the part number but all I did was look at the website for hagon in Aus and decided from experience if you want quality that works and lasts you have to pay for it. Hence there was no confusion on which shocks to get.
If you talk to your distributor and tell him you aren't happy with the cheaper hagons and that you want the Nitros with the 26kg spring, if he is a proper distributor he'll organise it for you.
As far as two up goes, you won't have a problem. In fact I took my son on the back for a 200km trip even when I had the 20kg springs on and whilst I knew they weren't optimum, we still had a comfortable ride.
So provided you have the 26kg spring you will be good to go two up as there is another 20 turns or so of the pre-load as it's now set at about 5 or 6 turns. In other words, before you go two up just wind down the pre-load as there is plenty to play with.
