Board query

[Wak]

Hi Guys,
I started windsurfing around five months ago and at this stage would class myself as a reasonable beginner/low intermediate. I am currently surfing on a v large Rio board with a 6.5m sail, both of which are hired on the day for lake surfing. I am now at the stage where I feel a need to part with some cash and have been looking at Rio Sport packages which I will hopefully be able to take with me as I advance. With this in mind I would be grateful if you could advise re sizes of board or indeed if I should be looking elsewhere within the range. I am 6'3 and around 95-100kg at present. Any and all advice would be gratefully received.
Regards
Steve.