Here's an update;
I bought some CS5173 devices and breadboarded an 18v converter. It works superbly and I can pull 500mA. These devices operate differently to what I'd assumed; You don't get a doubler - you preset the output voltage and the device maintains this regardless. So if you want 9v to 18v a simple resistive divider across the output sets the output voltage via a feedback loop where you need it. Now, if the input voltage drops, it maintains the output voltage and compensates by pulling more current from the input. For such a tiny IC I think it's pretty impressive. I'm mixing SMD and through-hole right now, but the circuit could be made really tiny with full SMD. The inductor is the only thing that's a little clunky - it needs to be relatively high current at 2A. All rather inexpensive, too.