Hydration Hack
Here's something I did.
Following up on Ivan's idea of mounting a water bottle behind the headrest, I got a Minoura SBH-300 cage holder and clamped that to Whisper's headrest frame, holding 2 bottles. Mine are Polar's 24-ounce bottles.
I got myself a length of silicone tube, cut it into equal lengths, attached those to a Y-junction, along with an existing drinking tube I had been using.
I cable-tied a length of 20mm-thick PVC tube (I sprayed it matte black from its original white), with a couple of thin strips of rubber, to the headrest frame. This serves as my taillight holder, handlebar bag holder, and drink tube holder.
The other bags on either sides of the seat were hung from 15mm PVC tubes (also sprayed black). Those are, in turn, held by pipe holders screwed onto the underside of the seat.
I've not used the hydration system as of writing this but I'll have a chance tomorrow when I ride in Singapore's hot and humid conditions (not that I drink a lot, though).
Whisper is turning out to be rather heavy, what with all the mods...!