Thanks Wapping/David/Engineer. Really good advice. I don't currently have a camelback, but sounds like a very worthwhile purchase.
They are good value.
I put an extension tube on mine so that it sits on the back seat. The longer tube I tucked under the edge of my Sargent seat. I can then trap the tube between the left hand switch controls and the light aux light switch on my 1200GSA. The mouthpiece curls round to sit inside the hand guard.
To stop the tube coming lose (it hits the road) I stuck velcro along it, to stick it to the underside of the seat's edge.
OK it gets a bit warm in the sun but water is water after all......
Flip front helmets make life easier on the move, too.