I have done this simple little test on my Classic-KISS last year and reported to the KISS list. Can't remember off the top of my head about the exact reason at the moment...
I made multiple 1" thick of layers of different grade and brand of sorbs. The scrubber is axial so there were quite a number of layers. Again, can't remember the exact number of layers...
Memory is the first thing to go as you age, isn't it ? Can't remember...
Anyway, what I do remember is it made no difference from the diver (me) view-point as far as WOB and duration. The scrubber lasted about the same number of dives and hours as when I filled it homogenously with the sorb recommended by Jetsam.
Take it as a grain of salt since I am not very "sensitive" about the supposedly minute difference on the unit when the parameters are changed slightly...
