I am running a ST90 on my proto-type Ecstasy with a long Mac Header and Mac tuned pipe. Completed aircraft weighs out at 7-1/2 pounds. I have taken some additional weight out of the production versions of the Ecstasy. It hovers at 1/4 throttle, and pulls out with authority at 1/2 throttle. As Jeff mentioned, you can check it out at:
http://www.hsrcm.com
The initial production kits are scheduled to ship early next week.
Kevin