Go into STANDARD/XCOM1/Soldiers.rul and change the max stat figure from 80 to whatever using something like notepad++.
same method
Stamina is your stat.
Ah now I'm so tempted to cheat... After so long, has anyone else done it this? Any repercussions? I'll want to be able to revert back to vanilla without feel pains.
The funny things, i remember, when i played first time, whit the first version, it doesnt have limitation to 80-81.