What negative effects will letting my thief wear studded leather +2?

None that I know of. If I recall correctly, only Elven Chain, Chainmail, Plate Mail, and Full Plate Mail will affect your Thieving Skills. Note that only certain combinations of multiclassed or dualclassed Thieves can wear the last three types of armour.

I don't have the BG book in front of me now, but I know in AD&D 2d Ed rules studded leather will subtract a few percentage points from some of your thieving skills. Only leather will not subtract any points from any skills. IIRC, wearing no armor gets you a bit of a benefit in a couple of skills - but I don't think this made it into BG.

Actually, I wouldn't think that Elven Chain would affect theiving skills, even if it's Chain Mail. It doesn't seem to affect mage skills at all...

I'm not sure but I read a part in the BG2 manual that there are certain pieces of armor that DO lower your [edit: skills.

[ 09-13-2002, 01:52 PM: Message edited by: philip ]

"I'm not sure, I am not sure"... Just wear it and check skills. Then take it off and recheck. Is it really worth posting?

So I did:
Studded leather armor changes nothing (I assume you are talking about thieving skills), but Elven and Drow chain mails do following:
Open locks: -5
Find traps: -5
Move silently: -10
Pickpockets: -20
I checked with pure thief, so I couldn't wear other armors.

Well hide armor also lowers thieving abilities, but who would wear that stuff?????

I found my SoA manual:

Thieving Skill Armour adjustments

NO Elven Hide Padded
Chain Studded Leather

Pick Pockets 5% -20% -30%
Open Locks - -5% -10%
Find/Remove Traps - -5% -10%
Move Silently 10% -10% -20%
Hide in Shadows 5% -10% -20%
Detect Noise???* - -5% -10%
Climb Walls???* 10% -20% -30%
Read Languages???* - -

* anyone an idea why these are in the manual since they aren't used in the game?

<font color="lightblue">Elven chain is bright; it draws attention to the wearer. A thief in Elven chain is a thief who will be noticed.
Howver, it is very light and doesn`t restrict movememnt, which is why it doesn`t affect mage skills. </font>