1 lbs a person is ok I think with Boston Butts and Picnic where you get over 50% yield cus that gives you a 1/2lbs per person or [2] 1/4lbs sammys.
Whole hog's yield is much less and I "think" around 35-45% hoof weight is yield meat. I may be wrong.
Take yer number of people and add 10% then calculate to giver yerself 1/2lbs of cooked meat per person. Especially if this is the only meat served.
Cook the 150lbs hog and 6 butts. Not all folks can/will take their meat straight from a carcas too. Meat's cheaper than hungry customers
Good luck