Cobaltbabe,
a good friend of mine is about your height, but model skinny. She dives the Diva in XS, and during the dive loves the comfort. But with 18# lift it barely keeps her at the surface, and squeezes rather badly. That aside, her tank (single cam band) came loose twice, and the velcro on the pouches start wearing low. The Diva LX seems to be the better BC when it comes to lift,
but is quite a bit heavier and bulkier when travelling. The only back bouyancy bc she found so far is the Zeagle Ranger Jr. (I'm not kidding, a kid's bc).
If you want to get into extended range diving, you might want to have a look at Dive Rite's Transpak II. Excellent quility, modular system, you might well be able to make it fit right for you. I know a couple of girls who dive them, and love them. Zeagle's BCs are also modular, and might work. Dealer's will (or are supposed to) help you fit them, for example combining one size shoulder harnesses and a differnt size backpad. Either manufacturer offers different sized bladders, so you can get them as you need them. Both offer well designed weight integration. The Dive Rite BC can be used with a backplate, it fits between the BC and backpad. If you can get it to fit you, I think it's the best bc you can get, and the most versatile one.
Good luck.
