Rigid vs. Pink & Fluffy

I have a quick question regarding the usage of different insulation products. Reviewing Bob Gold's site, 12" unfaced pink fluffy OC has just as good or better absorption coefficients then 4" 703. I assume that it reaches these higher values because of the greater amount of exposed area being that it is 12" thick. I guess that leads me to two questions... 1) Why would this not be a great product for superchunks? The coefficients are pretty even across the board and in a super chunk it doesn't need to hold it's shape that well. 2) Would compacting that 12" of fluff down to about 4" (seen in a few posts here) be as effective as 4" 703? I'm mainly asking because I'm getting ready to build the next set of absorbers in my CR and have much easier access to the fluffy stuff vs. 703. It's not really the money aspect, more of an availability/impatient/hate paying shipping issue. Thank you!

Each material has it's own absorption coefficient. The higher the number, the better for us :) Absorption is also measured at it's volume. When a 4" piece absorbs just as good as a 12" piece, you'd use the 4" piece. Imagen the absorption when making that 4" 703 as thick as the 12"pink stuff. no, you don't wanna compress it.