Some info from a guy that has been sailing maui for 18 years:
sailing the north shore here is similar to sailing out past the mile bouy in Santa Cruz. there are a few more of the force 7 days in a maui summer though compared to norcal. if you get down to the Paia beach and on the water by 8:30-9:30 in the summer you can sail in force3 building to 6 or 7 by 2:00. every day is different, but most wind patterns hang around for days or weeks in the summer.
sailing a beach cat in force 6-7 is kind of an extreme sport if you use sails for winds of force 1-6, but those are the sails you normally have. a smaller mast/main sail, say 90% of the current one, would be nice. it's on the list. for now we just roll up the jib when lazy or inexperience people are on board. we sailed from Paia 20 times in august and september this year.
in the winter we sail prindle beach kaanapali when possible. the wind is varried in winter.
i've only sailed southkihei-wailea areas a few times on a beachcat, but the winds are twichy there. sometimes switching from the left side to the right and back just like that. sometimes the wind can't decide if it wants to fill in from the La Perouse bay side or the Ma’alaea side. still a blast tho. you are better off sailing from the first canoe beach south of Ma’alaea. far from the Alenuihaha Channel. gateway to Tahiti, and purported to be the roughest channel of the islands.
hope this helps. you will be dealing with some potential dangers.