Few comments :

I think your prefered listing is P16, N500, P18 when I look at the describtion of your conditions.

Why ?

-1- the P16 hulls (keel line) cna be reinforced continiously by pouring epoxy in the V-ed kiel line. Also the V-ed keel line will hold up better to hitting a reef or rocks. Skeg boats are just a little more sensitive because of the protruding skeg.

-2- The strong weather will make the P16 a good fast boat. No problems of being underpowered relative to the P18

-3- I gave sailing lessons and skippered payed tours on a P16 with 500 lbs on board. The P16 will take it and not even sail badly. Of course a crew of two is alot better but still I really don't think that the P16 has a "problem" here. Of course the tramp space is getting a little small then (3 adults in my case) but Nacra 500 doesn't have more, only P18 does.

-4- The P16 is seriously lighter than the P18. Something like 30 kg = 66 lbs. This is very welcome when having to lift the boat over any rock outcroppings.

-5- The P16 has relative more righting moment to capsize moment. In a blow the P16 can actually be quite fast and comfortable to sail. It seems relaxed under those conditions more than my Prindle 18 (I owned both boats for several years). Nacra 500 should be the same as the P16 in this respect.

-6- keel wear is easier to repair in the Prindles, because of the V-ed keel lines and the large rocker the damage is always very localized and right on the keel line ridge. If you are really abusive then a layer of small class take with resin will get everything in order again. More rounded hulls and even skegs can present a bigger challenge.

Tacking ? Well none of these are boarded cats but the tacking is alright and comparable on all of them as long as you remember to slack the mainsheet a little in the middle of the tack. You will get the hand of that after a few tries and be comfortable with it.

Wouter