In reply to Sherpa Sheelah:
Numbers themselves only tell part of the story - there are so many human variations.
Proportion of fat to muscle in your 63.5kg?
Are you 'naturally strong'?
Do you have more fast twitch than slow twitch muscle fibres?
Wide shoulders, deep chest or all in your legs?
Are you flexible?
Do you have the basic climbing techniques right (i.e. resting on ligament, not flexed muscle, keeping your heels lower, moving your bodyweight well, balance, not freaking out and overgripping etc).
At your height, weight, age etc, if you're climbing 6a then (in real world civilian terms) you're already climbing well so probably have most of those non-strength techniques dialled, therefore wondering about gaining a bit of extra oomph is normal. Depending on those varying compositions above, perhaps you could afford to lose a little bodyweight, or equally it could be that you should stay as you are and not lose any. 5'3" and 63.5kg is not huge.
Power-to-weight ratio is more important than any overall weight number. Some of this is genetic, some trained. And by it's nature it is affected by bodyweight, but also, unlike genetics, can be improved by training. Unfortunately, it is one of our physical aspects that really suffers with age, so you can still be in good shape, have whatever bodyweight, but still not have the P2W ratio you had when you were 19, so some aspects of climbing will just be harder. Maybe you train more, maybe you improve other areas to compensate, maybe you be satisfied never climbing 7a, maybe you take up sailing instead - all perfectly valid responses.
In terms of basic physics, yes, having less weight to move up will make things easier, all other things being equal, which they rarely are. But climbing is almost never a clean mechanical lift, so such a basic equation means little (not nothing, just little). I'm tall and lean with strong arms and lats - and I long ago lost count of the number of shorter, beefier people with chunky asses and spare tyres who climb much harder than me.
As others have said, improving footwork will help a lot, as for most people at most grades. But at 6a, you're getting onto terrain that rears up much more than a VS so the weight will be coming onto your arms much more. Your fingers and forearms are little muscles to be holding the weight of *any* body.
Regardless of bodyweight, you may find doing some specific training to strengthen your arms, your grip and your lats/shoulders (for hanging) will help you. Your bodyweight probably won't change, unless you change your diet, as it's diet more than exercise that affects fat loss and overall body weight. A bit of finger/forearm training probably won't power you up over 7a but it will make you feel more secure at 6b and give you time to sort your footwork out
Post edited at 22:25