US Engines recommends 32:1 as the fuel/oil ratio. I use Echo 2-cycle oil with regular pump gas in my -41, runs great, better and better each time I fly it. I have run it at 40:1 with no problems, but 50:1 might be a bit light on the oil. Do you have the spring starter on yours?

I use a 16 oz. tank and get about 15 min. flying time with a small reserve. I have tried props from 20-6/10 to 18-6, but for my plane (22 pounds) 18-10 seems best.