From the accounts on allah and monkly-business, it sounds like he mostly (if not only) spawned in the 3rd spot. Regardless, even if he can spawn in any spot, he is far more rare than any account I've read on either site, as you can see by the quotes. Too frustrated to dig up more quotes, they all say the same thing as the quotes posted above man.
http://web.archive.org/web/200804051....shtml?id=6402
Overwhelming amount of quotes regarding the frequency of his spawn rate as well as location of spawn. Give it another gander.
I'm not asking for a 25% bump in his spawn chances Nilbog, I'm talking like...a little bit more. A 10 hour session should yield a fuckin' pipe is all.