Hi!
Well I dont want to sound like a "Mister Know it all " but I used the letter ! as a way of saying that: this is very impotant.

Yes tank size does matter. To large a tank means to high fuelpressure and this most engines could not cope with.
You will notice it when the engine could not hold it's needle setting from start to finnish and you have to set the highspeed needle a little rich at the start so that the engine would not go lean at the end of the flight.

Buy mounting the fueltank so that the centerline is horizontal with or slightly below the carbneedle orrifice inside the drum of the carb, one has a set-up that enables the engine to suck fuel without being subjected to too much variations in fuelheight (fuelpressure). Also by doing this one can also fly inverted
without having the engine go rich (or lean).

I don't use a fuelline filter on the engine. I use a large filter in my toolbox.

When I was on the Swedish pylonracing team in -95 at the World Champs in Muncie, Dave Shadel former World champ in pylonracing told me to never ever use a used washer because they can leak!

Most sport engines doesn't like more than 0-15% nitro as the nitro content raises the compressionlevel inside the engine.
Of course you could use more nitro but more than 15% usualy means that you have to lower the compression ratio by adding another head (0,1mm)shim.
More than 15% will only produce more heat and a finnaly distroy the engine engine.
I myself would never use more than 5-10% nitro in an OS.40-.90.
There is no reason doing that.

Well nylonspinner could of course be used and I use them sometimes myself on not so fast airplanes with small engines. But on larger (.40 or larger) I prefere Tru-Turn aluminum spinners or just a aluminum spinner nut!


Regards!
Jan K
Sweden