I was curious how much power I could get out of the converter.  The rectified output makes it very easy to measure. I just swapped the neon lamps for some 1/4 resistors.  This setup has an effective resistance between Vo_Positive and Vo_Negative of 100k. 

I powered it up, tuned the frequency, then cranked the power supply for the driver to 19V.  The output voltage rose to 236V.  This works out to 0.557W across the net 100k load -- not bad!  The power supply meters read 19V and 70mA, for an input power of 1.33W.  The efficiency works out to 42%.