Hi Dutchie
Model? Yak=Scrambler XT, Seat=High back classic, Camelbak (hydration pack) is the original had it for years now, having used it for mountain biking etc.
The only problems I encountered with the hydration system, which I have now resolved were:-
I fitted the hose through the seats top strap which restricted the reach, but now I can drink and paddle, move my neck at the same time!
The mouthpiece (bite piece) tends to leak a little so would suggest a cover bung which you can now buy or make one from a bit of rubber capping.
It all works well for my needs, you can even have a slurp whilst prepping up and derigging the Yak, just bite the tit and instant flow!!!!!
I have seen another hydration set up which I thought was neat, but not for my set up. Stephen Tapp has his hydration pack clipped on to the front hatch cover on his Prowler Elite, with an extension tube back to the small hatch midships. He just reaches down between his legs and grabs it (pardon the expression if you will). Looks to work OK in a long Yak. So where ever you want to place your hydration system seems that you can do so with extra tubing (from a pet shop?) but have some gravity with it.
Hope this makes sense
Cheers
Yak Fisher