I think one of the issues we had in the early days of the MK 8 was the absence of any ODM's! The aircraft came with a MTOW of 5300Kg IIRC and the performance data we had was from the Lynx Mk 3 S Gulf Mod which had a MTOW of 4800Kg.
Got to love the MOD's shortcuts!
(sorry if figures are out, memory is going back to the 90's!)