This is neat:
http://www.linear.com/product/LTC4412
It can turn an asynchrounous buck into a syncronous one as a drop in replacement for the diode, without support from the buck IC.
It uses a MOSFET (of our choosing) to do switching in place of the diode, but instead of being controlled by the main IC, it has a voltage sense. When there's voltage on the cathode, it closes the switch. The body diode of the MOSFET is used to cover the slight delay from sensing. This won't work for a 17mm version I guess. No room for the extra IC.
Anyway. I said before, and it's written many places, that max ripple current is at 50% duty cycle. As with many things technical that statement has to be taken in (a fairly unfair in this case) context. It turns out that's true for equal current. For equal power, the ripple as a percentage of average current is a bit worse or anyway pretty similar at high duty cycle/high output voltage compared to 2:1 operation. Most things though are easiest at high voltage output and get harder/worse at lower voltages.
I've been thinking about total voltage drop issues a little for 1:1 (now included in my tables), and adding some tweaks to the math. It seems to me on first scratch like it won't be an issue.