I've got the same bag, although I use it without the map case on front most of the time, I don't use it and find it just gets in my way. the front pockets are indeed intended for M16 type magazines, although they also fit standard Sigg waterbottles very nicely. The internal elastic loops are sized for 40mm grenades The foam sound like a good idea, I find mine tends to colapse when I haven't got anything in the main compartment. some foam should keep it's structure.
Just updated picts of my bags and what they carry: Belstaff 554 http://www.aaronlam.com/blog/2008/08/14/belstaff-554-large-colonial-shoulder-bag/ Belstaff 556 http://www.aaronlam.com/blog/2009/07/18/belstaff-556-colonial-shoulder-bag/ GoRuck GR1 http://www.aaronlam.com/blog/2010/12/10/goruck-gr1/
