I had my saito 91 running inverted w/ no problem. I pulled it off though. not enough vertical pull. I now have a ST90 2stroke mounted inverted. I haven't flown it yet. But I have ran a tank thru it, inverted and it doesn't seem like its going to have a problem.

I pulled the saito because vertical was lacking, it would pull out of a hover but very, very slow. I am problably like, DKJens, Iwant to be able to lauch out of a hover, not crawl.

I haven't had a chance to tach my ST90 w/ a 15x4W prop. But my saito 91 was only peaking it out at 9200-9300. and I had it set to fly at 8800. I am sure that the ST90 w/ stock muffler will atleast do 10,500. I am in the process of putting a moosecan on it. If the moosecan gives me the extra 1500-2000 RPM like it does on my other motors. That should put me in the 12,500 RPM range. That is 3700RPM increase in power. That is approx 30% increase in power over the saito91. That pretty good for a $50.00 motor that I picked up at a swap meet. Not bad.