I'm trying to do the lenghened moment arm versions of all my exercises. On the Pull-Ups and Chin-Ups I am a bit stuck. if I lenghen the moment arm on a chin-up it becomes a supinated straight arm pulldown. Scott said on my last post I dont need to that so I subsituted it for a neutral cable rope straight arm pulldown. But if I lenghen the moment arm on a pull-up (pronated lat-pulldown) it becomes a sort of side straight arm pulldown like the shoulders begin in an abudcted posistion. I see gymnasts doing this but my concern is this sort of iron cross exercise involves the lower chest aswell so is that a bad thing? 

Also whats the benefits of the wide grip pronated straight arm pulldown vs the neutral cable rope pulldown? Should I include them both or is the cable-rope on its own fine?

@MurkleMan I'm confused on a couple of things. Firstly, I don't really know what you mean by moment arm?

Secondly, you're talking about straight arm pulldowns - do you actually just mean regular lat pulldowns? Because they're two different movements. Using a supinated grip with a lat pulldown is fine, but with a straight arm pulldown you don't really need to worry.