Note: This procedure requires editing a game file; creating a backup copy of the file before proceeding is recommended. With a text editor, edit the "levelUp.sctipt" file in the "\Data\GameData\Scripts\" directory in the game folder. Find the line:
local newLevel = math.floor( detachment:GetExperience() / 100 );
Change it to:
local newLevel = math.floor( detachment:GetExperience() / 50 );
The number of experience points required to level up will be halved to 50. Note: The game will crash if you level up after the unit is level 5.