Yeah, if you really think you'll get cold fast, then go with a 4/3. i guess it cant hurt. but the downside is when you get into may and june, having a thicker wetsuit just ends up tiring you out more. or at least thats what it does to me. but its better to be tired and warm than cold.
with something like an o'neill mutant or rip curl insulator (both have detachable hoods), you should be good from 40° up to where you don't need a wetsuit anymore. as someone else said, better to be too warm than too cold. personally, once the water hits 40, i refuse to wear anything thicker than a 4/3 unless the air is ridiculously cold.
I would get a 4/3 if you get cold easy . Hyperflex , Xcel are really good suits . If you have the bread get a Patagonia R3 I seen guys out in December in a R3's saying they were hot
I seen them on special in a link on this site liquid board shop http://www.liquidboardshop.com/store/cart.php?m=product_list&c=52
if you are going with hyperflex, get a 3/2 amp. They are well made and extremely warm. On the colder days like in may you can throw a hooded rashguard underneath or i use their Polyolefin rashguard underneath and i'm nice and toasty. You'll be really warm in a 4/3 amp come june
don't mean to jump in on your thread, but it seems you got what you needed. im looking to get a suit for the rest of the cold season and will use next year. i was looking at the oneill mutant 5/4 and hyperflex flow 5/4. i can get the oneill for about 20-30$ cheaper, just wondering if you guys had any experience with em