Hi Steves
A friend of mine recently installed an IFA IVO Medium on his gyro and then took it for balancing. He ended up putting quite a few grams of weight on before it was balanced properly. This may be something to look at.
I fly a Vixen with 912UL and 72" IVO IFA UL and find it made a whole new a/c out of it. I now get full 5800 on climb out and much better cruise,
The only issue I have had is the small pinion in the center of the planetary carrier wears out quite frequently if you "adjust" too much. Big improvement over the GSC it replaced.
Cheers
Don