Another thing to consider might be that you will get a split in your fueltanks. With the S76b you can have an acceptable fuelsplit of 250 lbs. If the split becomes more we have to consider crossfeeding or shifting pax to get the w&b within limits. Crossfeeding in flight is in our sop an emergency procedure only. Single engine this split will be reached within 40 minutes.
The other thing you could do is swithching between the engines. 30 minutes idling engine #1 followed by 60 minutes idling engine #2. I think that you will be asking for problems as a mistake can always be made.
