I'm about 75kgs, have both the Naish medium and large wings, and have zero problems with early lift off...both SUP and prone surfing (+ wind and kite foiling). As JB suggests, check that your mast is perpendicular to your boards deck (and hence the fuselage and wings will be roughly parallel to the deck) A lot of retro fits / foilmounts etc also need a shim to tilt the mast forward. Once you get it set up correctly.... its awesome!
