Some of this might help you:
http://www.crimes-of-persuasion.com/mod … ngtips.pdf
LA seems pretty set on the 5'10" fashion thing now. Rare to see many under that height and I suspect some are cutting back on their talent pool as some of their online pages seem to be shrinking rather than growing (although some still have photos of people no longer with them so go figger? Makes them appear larger I guess.). I suspect their actual working base of paying clients is shrinking fast too so they may be hiring less and being more picky with who they do sign.
Some of the larger ones (the one you mentioned) are grabbing talent from the smaller ones so they know their talent's track record. How much pushing they really do is questionable in this economy, and they may 'push' only certain 'famous ones' to get more money - or the booker's favorites too.
You might have better chances with an agency away from LA, maybe San Francisco. Or just try Paris and see how it goes, but they might be the same or worse than LA too.