I don't know if this medically dumb or not but here goes. . .
Back when I was in Group
(when it was Hard
)
nobody used the waist band. Something about being able to dump the ruck fast.
OH the discussions generated about when, where, why to dump a ruck another thread perhap. . .
Anyway. . . A lot of guys added extra cushioning to the pad. I guess I subscribed to the theory that "if a little was good a lot must be great". So I found a nice piece of foam about 5 inches thick; I cut it the the width and length of the pad, waterproofed it and secured it to the pad. I liked it. I did not notice any problem (that may be a personal issue). What I did notice was now the ruck was an extra 3 or 4 inches farther from the small of my back. Soon after this we switched to the SINGARs radio and,lo and behold it fit nicely,horizontallyin the space created. The radio was totally accessable, the antenna ran up the frame and fully extended did not point to me and shout "Shoot this guy first!" I also found that a Camelback fits there nicely too. A med pack for an IV will too. I can tuck most any "nice to have quick" thing in the space. Like I said, it didn't bother me, I didn't notice a significant weight shift etc etc. I also didn't notice anyone else doing it and that gives me pause because conventional wisdom can usually be trusted. Especially in the SF community.
Or, maybe I'm really ahead of my . . . NAH! (oh and it made a really nice pillow for those poncho hootch bivs)