The guys who do use 7mm suits in the US as a rule are diving in conditions that would be too rough for a smooth cell exterior suit.
Just thinking outloud, i believe there is a misconception here...
North Atlanitc states are rugged, filled with hills, cliffs, boulders of granite ect. However, beneth the surface is a different world. All the rocks up here are covered in sponges, kelp seaweed or all three. And im sure in Cali its similar.
check out the beginnig of this vid of mine
[VIMEO]26880402[/VIMEO]
https://vimeo.com/26880402 = see? nice and cushy bottom to lay upon.
I dont think i need to show you guys how sharp and rough the bare reefs are down south! ouch
point is i am all for a smooth skin suit being added to your lineup! that instant dry feature is ideal for experienced(carefull) spearos up north and i have been using smooth skin gloves for the past three seasons and they are actually lasting as long as lycra coated gloves used in years prior.