G'day Mate.
First off a 10x6 is a 40 size prop, put an 11x6, & a OS 8 plug, to tune it slightly rich, run motor on ground, at full throttle, slowly turn high speed needle in, until the motor starts to sag, wind needle out, noting how far you turn it, until it starts to sag on the rich side, this is your tuning range, then turn it in, until it runs at a clean 2 stroke sound, this will only be a few clicks, & leave it there, but make sure you have no air leaks first. Hold the plane nose high & it should gain some revs, this is spot on tuned.