I've only had my BHID 300 for a couple months tried the hip mount thing yesterday and had the same problem. Also noticed that outfit gets heavy after a while so I'm planning on solving both problems by rigging up some kind of chest harness, I figure it should solve the weight problem and I won't have to hip mount the control box.
JP
I wear it on a nylon web belt and it hangs center of my belly, never have had it move unless I adjust it for better comfort.
Make sure you have plenty of coil wire loose so you don't pull it when using the detector