Yep, just as AH64DR says, we did use Supertigre GS 40's and at 4400' above sea level. the guys that knew how to tune 'em had 'em turning a tad over 18,000 with a MA Scimitar 9 X 6 prop. There were also those who were cheating by running MA Scimitar 9 X 7's that were clipped a tad. OH NO, now I've went and let the cat outa the bag!