Still don't know what you mean by RPM. In my world, RPM means revolutions per minute. It's a unit of angular speed and has no bearing on elevator trim.

for 3D I like my elevator trim to be totally neutral so the plane drops equally in upright AND inverted flight. If your plane is a good 3D airframe, with CG, thrust angle and incidences are good, you will also get very nice KE response (no coupling). Also, there will be no need for constant elevator input to torque roll only corrections as the plane falls off.