Is it correct that you have a Fu133, a AHD156 and a Formula ?
These boards are all pretty close to each other.
Unless you're into Formula racing, my advice is to sell them ALL and replace them by 1 Ultrasonic.
You' ll love it. Don't worry about jibing. The US does it like a charm.
I know a few lighter surfers like yourself who use sails as small as 7.x on it. No problem at all.
The board feels as light as a feather and can handle a huge range of sail sizes.
IS87 / IS101 / IS122 / US147