As to the S-92 range capability, it is a continuing puzzle to me that we ( well…Sikorsky ) never just copied what we did with the USAF H-3s and 53s and put external aux tanks attached to the sponsons. Not exactly rocket science.
Forgot to mention: as to the additional weight, there was a possibility at one time that an Atlantic SAR requirement might exist and that Portugal would be the operator of some S-92s. We prepared for this possibility by doing a flight loads survey flight test at 31,000 lbs and up to 9000 ft altitude ( and yes, including the rotor stall envelope etc - some interesting flying ). Anyway it never came to pass, but putting aux tanks on the sponsons would not be much different than similar experience with the S-61 and S-65.