Tzur, if i were you, i'd invest in sails. The boards you suggest will not cut it in waves you say you get (1.5-2 m!) and you may want to work on your stance on the board because if you need 18-20 knots to plane with a 7 mē there is something wrong. i weigh more then you and with a 7.6 i can plane 13 knots ... when i get the rare 20 i'm on a 6.2 and still planning so there's a slight problem there i think. I may be the front-footstrap thing.
THe 180 in waves? ok, i nearly drowned using the 139 in 3 m swell with 26 knots, i'm not sure a 180 in those conditions is a very safe option.
My primairy advice to you: work on your stance first, expand your sailrange then when you can plane in most conditions, buy a board that accomodates your sailrange.
Haiko, AKA crazychemical