I enjoyed my cooler testing experiments, and after finishing up, I decided on a 1/2 gallon Yeti Rambler for my hydration setup. My last hydration setup on the FJR used a 1 gallon Coleman, but I rarely finished the whole gallon, and by the time I did, it was warm water anyways. I expect that the Yeti will require much less ice and keep the water cold all day for me.
And here is the finished project, installed on my BMW K1600B:
Yet offers a Jug Mount accessory for their Yeti Rambler Jugs. The Jug Mount is basically a plastic basket with metal reinforced holes for mounting. I had a fabrication shop make me an alumimum mounting bracket that takes the place of the left side passenger footpeg and holds the Jug Mount, using it's existing holes.
To complete the hydration system, I drilled a hole through the Yeti Rambler cap and took out the cap magnet. A rubber grommet seals the hole around a length of 3/8" rigid poly tubing, which is connected to 3/8" PVC tubing with a 90 degree elbow. A Camelbak bite valve, an insulated sleeve, and a few zip ties finishes the installation.