Does the engine run away? Is this a brand new engine? I also see you added castor. You didn't mention if this is the iron piston or the ABN version. I would certainly make sure if the o-ring under the venturi is good and intact and that the venturi isn't wiggling. In either case I certainly feel 22% oil is suitable without the added castor,  although others feel you need the additional oil.  How does the diameter of the ST spraybar compare to the stock OS spraybar? Are you losing choke area due to this? I never used the ST spraybar so I'm just asking. Is this the extended ST needle? I've seen those needles act like a tuning fork when they're sticking out. Hold the needle while it's running to check and see if the run changes.  Are you using the stock muffler or tongue muffler? I prefer the Randy Smith tongue and I don't drill any additional holes. I just open the holes up to 3/32. Is the engine in a full bodied plane or profile?  I use a APC 10x5 on a Brodak .40 with consistent results. I believe the APC just has much more weight than other props of the same size.  This doesn't mean that this is the prop for the FP.35. You might have to go with a  APC 10.5 x 4.5 or like a Thunder Tigre 11 x 4.5 pitch prop  and run the engine at higher rpm's.  I know many that fly the FP.35 claim that it's more friendlier than the .40. Did you add any head gaskets? I certainly would start with one additional head gasket and go from there. I use uniflow tanks and I achieve good results hooking up the muffler pressure to the uniflow vent. Others just allow the uniflow vent to the atmosphere and get terrific results. This generally doesn't work as well for me. On another note, your not describing exactly what kind of run problems your having. Certainly start with trying to inflate the tank like your trying to pop it. Check underwater for leaks. A vibrating airframe is certainly going to make all kinds of havoc and this can take all kinds of experimenting to achieve good results. A simple thing like a shot or two of Armor All in the fuel might just yield a good run. Ken

      Randy, I'm using a tongue muffler with 3/32' holes that are tapped to 4-40 if I need to restrict it.
 What other info do you need to be able to suggest gettin a consistant run??