Rick,
which under armour are you using?
There were a couple of mentions but not much attention to UA. Since it isn't made exclusively for diving, maybe some guys aren't familiar with it. I'm a high school teacher and it is all the rage with high school/college athletes.
I just bought a new set of Under Armour a few weeks ago. I've made several dives in the 38-43 degree F range and haven't been cold yet.
Here's what I'm wearing:
Under Armour Extreme Weather Base 3.0 pants
Under Armour Coldgear Metal Shirt
Cheap drysuit undergarment (don't know weight, bought it used for $30, when turned inside, looks like I skinned a wookie), probably the equiv. of 100 or 200 gr thinsulate
Viking arctic socks.
7 mil hood
5 mil wet gloves (dry gloves on order)
That's it, not bulky at all, great range of movement.
I've made several dives around 1 1/2 hour with them and don't get cold. I'm a warm guy and don't get cold easily but the Under Armour has definately added warmth and comfort to my diving. It is a bit pricy for underwear ($150 from Cabela's) but it is machine washable and extremely thin. I didn't need to add any weight to my belt.