For what it is worth I did not put any out thrust on a three engine Kadet Senior. I have been flying on outboards only for most of the last 12 or so flights. The last four flights have deliberately been with mid range synchronization off by 1200 RPM (7200 and 8400). There is remarkably little difference in flight characteristics.

For experimentation I prefer to shut one engine back to idle in the air. It just seemed safer to have the protection of being able to throttle up if things started going haywire. Needless to say the switches sometimes get flipped the wrong way and one engine will shut down.

In my opinion the key is to acquire engine out experience in non-emergency time and with an inherently stable airframe.

Bill