Iam an experienced pilot, this is my sons plane. I have removed the flight aids he will be fine with a clean airframe.
He has a lot of talent and some stick time with one of my other planes.
I too am thinking of using an OS46, probably and FXI will pick up from my buddy Bruce Fischer at brucercengines.com, Ihave gotten several from him and they were all awesome, he tests all his engines before selling them.
The engine mount restricts the number of engines you are able to use with the vibration isolators, my Irvines wont slip in or Icould use my well worn 46 on it.