Ah- if you're seeing differences in torque between aircraft, there are several possible causes - torquemeters not calibrated (I assume they're oil pressure type torquemeters, not electrical shaft-twist types), different blade cleanliness, different blade balancing setups, etc.
I was able to prove to the maintenance folks that the torquemeter pistons on a particular Bell 212 weren't right because we had a prototype power required to hover calculator that showed we were off in torque required by about 5% - they didn't believe me until they really checked.
Remember that torque is drag on the rotor blades and any differences between blades, such as bugs, or other build up will change the drag.
I think the civil S-61 doesn't have trim tabs, but if there is a large difference in the way blades are set up for tracking and balance, (are pockets moved?) that can make a difference.
Good luck!