wetsuit for cold water

[subzero]

Just wondering if anyone has any thoughts on brand of suit to buy and also whether I need to go 7 mil or if 5 mil will be adequate with hood. At this time, I have a 3 mil full and 2 mil vest with hood. I dived Maui a couple of years ago in late December and the 3-2 worked pretty well in water as cold as 71, but I'd hate to get on the boat and find out on the first dive that I'm too cold. At age 60, the old circulation has slowed down a bit, and I find that I no longer need the A/C to keep the house below about 74 F., so a little warmer probably is better.

I normally dive mainly in the Caribbean, so I don't have a great deal of experience in water colder than 80.

[Jack]

would tend to err on the heavier side instead of lighter if I was needing a wetsuit.
Advice-wise, I would go with a good-fitting 5 mil, and take the vest with. If you're doing multi-days, or a liveaboard, that could come in handy.
A 7-mil in 70-ish water would probably be a little TOO heavy, especially if you're good in a 3/2 in 71 degree water.
The hood will really help a lot, BTW. Wear boots and gloves, and you will be comfy, I think.