[Walter Atkinson]

Gentlemen:

The answer is in the science. There are two things required to achieve max range.

1) Attain the best L/D airspeed (someone said that's 100 knots in a Skymaster. I cannot confirm that, but suspect that's very close.)

2) Set the mixture to BSFC (min). This will be at a mixture of about 15dF LOP at the very low power setting required by having two engines running and at 100 knots. With one engine running BSFC(min) will be 20-25dF LOP since the single engine will be putting out more power.

BOTH of these actions will result in max range AND max efficiency.

Personally, I would choose to attempt this with both engines running and I'll be quite surprised if the single engine scenario were better. Running on only the rear engine is likely to alter the angle of attack at the slow airspeed to a less efficient drag condition. Testing would be necessarly at the expected flight weights.