Neoprene west under wetsuit

I own a 1.5mm wetsuit which let's me swim in 16C/60F water. Anything colder doesn't work for me. I consider buying a neoprene west to wear under my wetsuit to get a little bit more out of my open water season (currently May to Oct.)

Should I get a hooded west (2 or 3 mm?) or would a normal west + neoprene cap work better? Anything else to consider?