The 2.4 is a gasser no? It has no place in a 67 inch plane.
The 150 wont be too much and the 120 is enough.Not sure on weight but a YS 140 has much more power then the others,and is a superiour motor for aerobatic and 3D flight and will fly more choices of aircraft in the future.I know it costs a bunch more,but I doubt you'll regret it later.If you dont intend to fly beyond sport aerobatics style, then the OS 120 or Saito 150 will work excellent.Perhaps a Saito 125?