I think I really want to let Yoshimo out and then get him later. I want to take Korgan but realize he is evil and my party is mostly good. So I thought, maybe I should try this nifty Conversion spell to supposedly change his alignment. Maybe just to neutral. I'm a little wary, assuming he would have evil quests that are scripted in. Anyone ever try it? I really, really want to get a pure tank in my group but don't want to mess up the game. Thoughts appreciated.

Even if it worked I'd have to decide to let go of Minsc, Jaheira, Aerie (romance) or Adario (my assassin) to take him back so I could have Korgan in the Underdark. And Jaheira has some nice spells in TDD. Decisions, decisions...(I can't get back to Akthala after Spellhold right, until after UD?)

I was unaware of a spell like that in TDD. I've written one myself. I'm curious as to what effects this spell has (besides alignment change)...

As for your initial question, I highly doubt alignment shift would matter in a non-romantic situation with an NPC.

Well, I might be assuming it is TDD, but that's the only mod I have and I never saw it my first time through. It is a cleric spell, with the green ink, like the protection scrolls.

So you think even if I changed Korgan, it wouldn't change his purpose and my party might still wind up getting mad? (I've never used him before.) I'm going to take him up on his Graveyard quest and at some point, convert him and see what happens.

I've used it on Viconia, non romance, and all that happens is that she gets happy when your rep is high, it's a useless spell RPing wise (no char development), and marginally useful gameplay wise.

I tried to use this scroll right after I picked up Korgan and something strange happened:

"Party has gained experience 6000
Party has gained experience 7000"

Now the spell is in Aerie's priest spells but she is too low to use it. I want to keep Korgan, but after this Kaza book thing, I know he'll leave because my rep is too high. So I guess I could change his alignment in ShKeeper or lower my parties rep.

Something's funny here. Adario the assassin is the most evil member of your party. Why aren't you trying to dunk him in the holy water?

Because Adario wont leave if you have a high reputation, but Korgan will...

the funniest thing, i've NEVER had an evil npc leave the party because my rep was too high, they just complain a lot, and i dont think i've ever had a good one leave , but i've never had keldorn in a nasty party. i would really assume he would take off if i was massacring everything, i just never do when i play a party with a paladin in it.
however i have several times had 20 rep with a evil party, just because those quests i know the best, playing this game so many time. like i said before, lots of vocalizing, but no leaving.
i remember in bg 1 folks leaving because of rep disagreements though. maybe i am just the lucky one?

high charisma reduces the chances of them leaving

If you had a rep of 20 before they joined and after they did, your rep didn't drop, then they complain but don't leave. If your rep would've drop, even by 1 point, they would have left.