Hi Sharkely,
In terms of accounting for realism, can I make a suggestion? Weight the tonnage by the realism factor. For example:
Player 1 plays at 100% realism:
2500t x 1.0 = 2500t final tonnage
Player 2 plays at 84% realism:
2500t x 0.84 = 2100t final tonnage
Player 3 plays at 27% realism:
2500t x 0.27 = 675t final tonnage
etc. etc.
Of course this requires some honesty on the part of the player, but the idea is you are 'rewarded' for playing at higher realism, and 'penalised' for playing at lower realism. Higher realism is more risky than lower realism, but the rewards are better so it should make for interesting results.
Good Luck