I don't have any tach readings but have had good luck with the Valentine turbo and standard plug glow heads on Medallion .09s in general sport use. Since the stock heads were getting pretty hard to find when I aquired my first .09s, I just flew with plugged heads from day 1. I know this isn't the hard data you were looking for but I'm just sticking it out there for folks who just want a reliable setup without the hassles of searching for Cox replacements. It seems that the glow plug doesn't hurt the performance as much as it does on the smaller displacement .049s. Just MHO. I plan to fly one of them tomorrow, though the winds are forcasted at 20-30 and gusty.

BTW, I just love the raspy, snarly sound of a Cox .09 in flight.