I have noticed that there must be something wrong with the Proficiencies and I don't know at the moment if it might depend on the BG2 Fixpack or if it's BGT.
However, I created two characters:
The first is a F/M/C with Proficiency in Flail (2 stars), Mace (1 star) and Sword&Shield Style (1 star)
The second is a Skald with Proficiency in Crossbow (1 star) and Two-handed weapons Style (1 star)
For the first one, if I equip the Sling (which has its own category), I get no penalty (THAC0 remains the same).
For the second one, if I equip a Short Bow, there is a THAC0 improvement like if she was specialized with it.
I had only BG2 Fixpack (all components installed) and BGT 1.04 just to make sure that other mods couldn't be interfering.
Can you please run a small test yourself and tell me if you can duplicate it?
Thanks!

P.S. Since I have two OS, I can run more tests for you if you like, Ascension64. Just say the word...
Edited by Salk, 05 July 2007 - 04:05 AM.