Cheers guys.
Didn't want to run a camelbak as worried about chaffing or back/shoulder issues after 24 hours.
I've got a crew, in fact, Team Syncros have agreed to take us under their wing and help my crew as they're first timers. I figure one bottle should see me two laps and we should be trackside so I can grab a new bottle every two laps.
Obviously I'm banking on a dry race and no mechanicals and won't be needing the spare bike, but figured I should find and test a solution before hand.
If gaffer tape, lagging and zip ties doesn't work, I'll try some of those other suggestions.
ADH: seeing as the spare bike is my Five, imagine the amount of fluids I could fit in the downtube/swingarm!