I originaly flew mine with a YS91 AC. It flew OK but would not be strong enough for the taller maneuvers in 402.
I have had the opinion that a YS120 was not stronger than a YS110 , just heavier.

I still vote for the YS110.

If we didn't have to deal with a 1 piece wing, my 1st choice would be for an OS91FX on a Looong tuned pipe(26inches from glow plug to 1st baffle is what I remember). Definatly lighter AND stronger than a YS110. It'll turn a 14.5X11 4blade APC . the YS110 struggles to turn a 13.8X10 4blade APC. BUt that setup is also getting expensive.
Eddie