Just to confuse matters more, my calculations came out at +4, IIRC, and the +6 was included because it was the official value (as are all the original DMG values).
I agree with Knight Otu that a +4 is penalty enough (compare it to the +5 Ogre, for instance).
That's the funny part though. +6 was never the official value. In the FRCS, it's +2. In the FRCS errata, it says to change it from +6 to +8, but it was never +6 to begin with, and the Kir-Lanan isn't in the DMG either. It's a FR monster.
Soldarin said:
I agree with Knight Otu that a +4 is penalty enough (compare it to the +5 Ogre, for instance).