Space Walker "ARF" what engine??
 

Saito 100 twin should be great for this plane. The noseweight should help balance it without having to jam everything up against the firewall and/or add a bunch of lead. Sound will be super, too. BTW, I don't understand why Horizon is recommending 12x8 to 13x8 for this engine, though. It should be able to swing a lot more wood than that.