Just upgrading the transistor Q2 from the stock PN2222A to 2N3866 (metal) with the heatsink borrowed from my Super Tuna Kit has yielded an increase in output power from 275mw to 355mw, relatively speaking, without touching the 56-ohm emitter bias resistor. There is slightly more gain in the upgraded part number. We were cautioned in the Buildathon not to reduce the 56-ohm resistor to zero without close monitoring of the temperature of the transistor. I bought a whole variety assortment of trim pots and have clipped off one leg to install it in place of the stock R7. It measures a minimum of 2.2 ohms to ~113 ohms, so it should yield good results in obtaining that near 700mw goal. I do have a couple of versions of the Tuna Topper, so controlling the input power to the final amp would make it a useful feature.
David Knapp