I find that any gauge higher than 9's need and extra spring otherwise you gotta turn the claw in alot. Also with a guitar that old your springs might just be worn out too. I have solved alot of tuning stability issues with replacing springs with others.
Dont' forget the chapstick on the knife edges too. That little trick does wonders. You should read the tech section on
www.ibanezrules.com just click the banner up top. There is alot of good stuff there on how to setup ibbys.