W0lfster,
I thought I did answer your question. I say yes...(UTG) is the perfect position for a straddle. Why not? Chet is correct about house rules but, I can't imagine anyone that allows buying the button in a Mississippi Straddle game not allowing a straddle from anywhere!!!
I've exhausted enough energy on this subject. I said on my very first reply that I've never seen it, and I'd never play the game... so my comments are not based on experience, just logic.