I have been able to attach my old original Camelbak holder (c.1996) that has clips built into the straps (more recent models don't seem to have this feature anymore) directly to the seatback frame of my recumbent (Sun EZ1-SC-Lite). I also got the underseat pannier rack option, so I can stash extra Camelbak bladders in the panniers on really hot days and the center of gravity will be very low and stable. This is working well. I don't notice any instability with the Camelbak there on the seatback. I really don't notice it being there except for having easy water on tap of course!