Oil return line connection

Is he engine level length wise? On the ground or in flight, pick the lowest point to get all oil returned to tank.

Yes, let's assume that the engine is level on ground and during cruise. A little down pitch may be within the mount. However,  I'd think that it won't be an issue. During steep climbs with high power setting the wrong (too high) connection may be a bad choice (which I regard the basis for the recommendation in the IM).

But are we talking about something "less than best" or "killing the engine". Would the wrong choice result in higher temps or get the oil to its operational limits?

Has anyone performed a change from front to back position of that connection or vice versa. Where there any particular findings resulting from the switch?

I'd use the one that's on the lowest end during a climb to keep the oil tank fed.