I have a SiG kadet lt-40 Kit.
I am planning to buy an OS 52FS
What is the Prop i should use for running in the engine?
Can i use a 12X4 APC?
Also i would like to have the slowest possible speed.
Do you think that a 13X4 it will be ok for 52FS?

!2x4 is a bit light -12x6, 12x7, 13x4 or 13x5 would be good.

Prop it to do 9500-10000 static.

I like the APC 12-5 on mine. They pull a APC 12-6 OK at around 9600, I just like the 12-5.

If you want it to fly slow, throttle back some.