Hi, I tried your mod and did a little trick...
I used the console cheat player.setlevel 19
to see how much xp is needed to reach level 20 and it's not as slow as everyone may think.
XP NEEDED FOR LEVEL 20 :
------------------------
vanilla : 29450
Koldorn's slow levelling : 42275 (1,43 slower)
Koldorn's slower levelling : 55100 (1.87x slower)
Koldorn's very slow levelling : 63650 (2,16x slower)
Xodarap777 XFO_Pacing_high_(slowest) : 72200 (2,45x slower)
my first character savegame is : Save 116 - Salma Hayek, Launch Control Bunker, 103.33.48.fos
I played from the start on very hard and I was level 20 after or 70-80 hours and now I stopped playing while I still had things to do in the game.
I now started a character with very slow levelling and my hope is to delay the levelling enough that I will be able to enjoy the full game without hitting or barely lvl20.
I currently don't believe in balancing mods, the game is pretty good from the start and the current attempts are ruining the game more than enhancing it, but hey I only play fallout 3 5-8 hours a day I really wouldn't know