Mark _australia said..
BTW for the nay-sayers it is fine.
16-18kn and my 98kg and it was easy planing. Very easy
I use 'Windsurf Calculator' and 'Windsurf Buddy' on my android phone..find them fairly accurate.. They both show around 18kn for 98kg and 7.5 sail...given your experience and as you have proved 16-18kn is not surprising. Did you need to pump to get planing?