The board is designed to best accomodate a 7.5 - 8.0 sail for an 80kg sailor in winds around 10 -18 knots (my guess). 18 knots will be a handful for most novice and imtermediate sailors on this board.
It depends on your sailing skill and experience. Also the type of sail - No cam freeride or cambered racing sail.
Assuming an average of 15 knots with holes and gusts, a no cam free ride/race sail and your 76kg -
Novice - 5.5
Intermediate - 6.5
Advanced - 7.5
My suggestions (give or take 1/2 meter) - others may offer some additional recommendations.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.