Also, I don't like wearing a CamelBak backpack, so I decided to incorporate the bladder into my foam design.

The white foam is quite dense, almost like styrofoam and is almost 2-1/4" thick.
The gray foam is much softer and is just over 2-3/4" thick.

Cutting the foam was quite easy once I employed the correct tool--an electric carving knife!
My wife isn't real keen on receiving it as a gift...I don't get it.  8<(

In case the bladder ever leaks, it goes on the lower level.  I also cut a path for the tube.	For the next level, I managed to filet the white from into ~1" thick halves.	Half stays intact as the barrier above the bladder, while the other half will serve as part of the upper level.
From bottom to top... The intact ~1" half; The other ~1" half with cutouts for my gear; Full thickness grey foam cut to match the upper white half. The discoloration between layers is the contact cement I used to put it together.	As shown... The left slot holds the Zumo 550; The camera spot is obvious; The lower spot is for my prescription, reading, and sunglasses; The rest just hold misc junk I carry.	All of it stacked, including the lower/bladder layer. It's far from perfect, as the bladder layer is a bit larger.
All of it in the tankbag.	Zips closed just fine with all of it in.	Without the bladder layer, it sits lower and will accommodate even more misc junk.