My wife is small, but not quite as small as you are. Every BC she dived in would slide around on her. Until she got a DiveRite TransPlate harness and steel backplate. She won't dive with anything else any more, and otherwise isn't at all into dive gear. We recently went to Palau for warm water diving, and I figured she would be overweighted with her regular steel backplate, so picked up the stainless steel DiveRite XT Lite backplate and another TransPlate harness. Added the DiveRite travel weight pockets and her single tank adapter and everything was great. You can also get a backplate pad so there isn't just the steel backpate against your back (my wife likes this). This works great for purely recreational diving, and my wife enjoys diving a lot more now than she used to