Yeah, thanks Bob! I like to use the D9 in my Thrustline Arapahoe-E; it has a nice long burn, but keeps the altitude low on the small field I sometimes fly from.
This is a light, low drag bird designed for an E9, so I thought a D9 would be fine, especially given the lighter weight. The first time I used a D9, it lifted off very slow and did loops, hitting the ground under power, though little damage due to the deep snow. I was mystified, since the Arapahoe-E should be plenty stable. I added a couple washers to the NC, and it has flown fine since then on this motor. All the loads are about the same age. I'll make sure to sand the grains in the future.