So I've bought a 20yr old 150 litre formula racing board Kinetic Centurion 2 designed by robbie radis.

Im kind of a beginner but I want to go fast. I'm 110kg. What size sails do I need to get me and this board screaming across the water? I currently have a 5.5 but I think it's too small. Looking to sail in average winds in Perth.

Perth based. Thanks guys

I had one and used a 9.0m with it. Never liked it. I'm a very experienced sailor and found that board way too extreme, its just full on all the time. Its a pretty extreme board for a beginner. I dont know what your financial situation is, but I reckon that board will impede your progress, and there are a lot faster boards for someone of your level. But I'm only one opinion see what others have to say.

Use it only in marginal winds as the chop will kill you in above 15 knots.

Need a carbon 62 fin or bigger.

Rig it with a 7.0 rigged very full or with a 7.8 with more downhaul.

Could work great as a stand up paddle also.

Get a 80 cm wide slalom board with around a 44 carbon fin - will feel a lot nicer in the chop.

Beginner to windsurfing completely?
If so stick with that 5.5 when up hauling .
the above advice from PC will be for a bit later when starting to plane

Formular boards are not for beginners. Back in the day, the quiver for formular was 9.8, 11, 12.5. although an 8.5 would get you going.
70 cm fin was standard. Designed for upwind downwind course racing. If you had an 8.5 and 65 cm fin you could get it going nicely on a beam reach. Formular boards were hard work. Agree with PC, big slalom board and 44 fin

Yes but for non planing learning they're perfect as they are stable and cheap now

Give Mark a call when you smash the nose it, its highly likely going to happen.

Those boards do get going early but are renowned to be fragile especially when catapulted.

I hope you do get to enjoy some speed but it would be more comfortable on a free ride board.

I got formula kit when I was just able to plane in the straps and don't regret it. It was challenging but helped me to improve. Also a lot of fun in the right conditions. Should use sails around 10m, you get used to them after a few sessions, make yourself an 'easy uphaul', just a loop on the uphaul that you can hook to your harness. A carbon fin also makes it more fun, the board will feel livelier.Disclaimer:
I live in NSW and am much lighter than you.Also had smaller boards for stronger winds