I went with the Saito 125 and flew it yesterday.

I'm pleased to report that it gave me the performance i was looking for. I'm still running the engine rich but it was turning an APC 15x8 at 8,800rpm.

The model now has unlimited vertical and I found i was cruising at around half throttle and increasing throttle for the climbs whereas before i was at full throttle most of the time and would run out of puff in the vertical manouvers.
It tracks much better through the air and my aerobatics were improved. I was able to knife edge the entire length of the runway.

I don't know whether that's because of the greater thrust, higher propspeed or the extra 2oz of weight in the nose.

I'm pleased with it.