When I worked on boats in the Carib. I would wear a 3mm full suit with a 3mm hooded vest. If I was too warm, flush some water in. If I was too cold, pull on the hood. On a live aboard you'll be diving 5 dives a day. By the middle of the week you'll be getting cold allot earlier in the day and the dive due to thermal deficit (SP?). When I worked in the Keys I had a 3mm farmer john and a 3 mm shorty. The full suit and hooded vest seem to trap less air and feels warmer. I'm pretty skinny, if this comb. works for me, it should work for you too. Longer surface intervals also seem to help get your core temp. back up after a dive. Most people only stay out the min. the computer tells them before they head back in. They also tended to dive to the limits of the computers, air supply permitting, in most cases. They never seemed to fully warm up from the last dive before going back in to start the heat sucking process all over agian. By the night dive you'll be getting chilly in 20-30 minutes on Wed.