I just started running my Echo 21 again. I tached it at 6500 with a 16 x 8 mounted. Static thrust was 8#. My tach started acting up so I did not get a good reading (didn't sound faster) on the 15 x 8, but the thrust was down to 7# and the flight performance was measurably down. I am interested in performance mods so I will check out the referenced threads. A couple of years ago I had about 15 to 20 thou shaved off the cylinder body to increase compression ... seemed to help, but no hard data.

Ain't gassers fun!

Bedford