Hi people, I made a small script to multiply the gain of XP by 2. work on the GOG version.
So I recommend it if you have finish the game once and want to maximise Characters without really "cheating".
-I did it after spending many hours on the different difficulty modes and farming bosses to unlock and maximize all the spells and feats of the sorceress. Level required to unlock all spells and feats by caracters
Elven Sorceress level 38 / 735 skill points*
Human Archer level 32 / 515 skill points*
Dwarven Fighter level 24 / 297 skill points*
Drow ranger level 26 / 214 skill points*
*I hope I didn't make a mistake in my calculations .