G'Day Alstack,

Please keep in mind that the Contender is a relatively heavy plane. I have an OS .46 FX in mine but I needed an 11x7 prop to give it the pull I needed. A .60 sized engine would be great (though you will have to carve out lots more cowl

A 2-stroke will give you more speed but the 4 stroke will give you more pull. Depends on the kind of flying you want to do as well. Basically the 4 stroke will swing a bigger prop.

If you do a search on "Contender" you'll find a thread that talks about various mods that will benefit the operation of the plane.

Good luck

Nuker