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.

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

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

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