Assuming that a HCH II can be operated using roughly the same principles as a normal car...

From an aerodynamic perspective, you should be fine up to roughly 60mph before the drag losses begin to get really nasty. So your around town steady-state speed shouldn't matter too much as long as the CVT cranks up to a high gear ratio.

IMHO, the real trick to 'hypermiling' in any vehicle is managing the transients: acceleration and deceleration. Minimize both! You lucky hybrid folks have the advantage of regenerative braking, which really helps. But it isn't 100% efficient and can only provide so much stopping power before the friction brakes kick in. That said, every time you stop you bleed off kinetic energy to heat one way or another, which is somewhat like splashing gasoline out of your tank. You have to accelerate to re-gain your speed, and that takes a whole lot more fuel than steady-state cruising no matter how gentle you are with the throttle. IMA helps, but again it isn't 100% efficient. That energy may be partially recovered braking losses (good) or it may be from a recent forced regen if the pack level got too low (bad, because that is a lossy process).

So accelerating gently and cruising at a reasonable speed are a big part of driving for efficiency. But planning ahead to minimize energy lost to braking and subsequent acceleration are even more important, if my experience is worth anything. As the sayings go: drive as if your brakes have failed, and pretend that there is an egg between your foot and the accelerator . You have to be very in-tune with your surroundings to do it, which keeps you safe to boot!