[mschuep]

Randy, as far as your question on 1/2" vs. 5/8" GWB, I would have to do some research to give you a difinitive answer...

My feeling is that, theoretically, you are not going to see a whole lot of difference...At least when it comes to an official IIC or STC test.

However, I would think that in general, the 2 x 5/8" is going to isolate better than the 2 x 1/2" simply due to the fact that it has more mass. More mass means more attenuation, especially at low frequencies. But, compared to the overall assembly, it probably won't have a noticeable effect.

It is likely to be dependant on the specific assembly, and the airspace depth, type of GWB, etc.