Just a mention... You may consider getting the case Tig welded as it's pretty much a full strip down of the engine. It's a proper job done then
although I will agree with you on tig welding the case ?, but !. not everyone knows or has access to a tig welder next door ?, not to mention, it won't come cheap by any means !..lol. but yes, you are correct. heck, even some one that does aluminum welding will work very well. had this issue pop up on my buds trx500FPE cases, he had a guy do some aluminum welding to build up the oil drain area, worked pretty good. again, you are correct, tig welding is the way to go.