Well, if you go with OS or any other brand of that size,your going to have the same problem. The 4* 60 is a 7-8 lb plane with a 71 inch wingspan. I have no idea what prop your using but I am sure it only adds to the problem. You simply have a bad combination and your underpowered for the size of the plane.

Separately, you have a good plane and a good engine. As far as it not shutting off, that is simple adjustment. Whoever you have as an "advisor" is not doing a good job.