Hi _liam_
Great to see you got a DRZ, really from the type of riding it sounds like you will be doing there isn't any other choice.
On my last DRZ I used to run the bigger front sprocket 15 up from a 14 and a smaller rear 44 down from a 47 this gives you the same gearing as the street version of the DRZ which will sit on 100km/h with ease.
Keep riding and remember to give us a shout when your after someone to go riding with, I am no supercross champ so you don't have to be Chad Reed to keep up to me

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Also the link Paul posted
www.gearingcommander.com is excellent for working out RPMs on the DRZ.
Andrew