I dove yesterday in 47-degree water. I had a 3mm merino-lined Pinnacle torso heater under a 5mm farmer john (beaver tail jacket) and a separate hood. It was tolerable but not by much. The one spot that bothered me the most was my upper back, and I'm thinking if I just put a hooded vest over what I'm wearing, I'll be in good shape. I do not intend to dive any colder than upper 40s. I'm looking at a 7mm Pinnacle hooded vest. Is something like that designed to go over or under a suit? Probably a dumb question, but with the hooded vest, I don't use my regular detached hood at all, correct? The other vest I'm looking at is the Bare Arctic, which I understand is meant to be worn over a suit, but that one is twice the price. Assuming I go with a vest over this setup, how do I choose a size (online)? The torso heater is a medium large, the farmer john is custom. I'm thinking a large vest will do it because the dimensions on those are a little higher than what I'd normally buy.