I find magazines mounted on the actual drop leg (shroud of body of the holster) to be almost unusable in a practical manner, have them on all my 6004s at some point. Think about trying to remove a magazine with your non-gunhand and you will see what I mean, the reach over/down is bad enough when you are just in a shirt but start adding layer of clothing, body armour/chest rig etc you are getting toward the work of a good contortionist. They will better serve you on your chest rig of offside. In addition to the problems getting them out also consider the issue highlighted above about the fatigue/discomfort already associated with a thigh rig (particularly when walking long distances) and consider the implications of adding MORE weight to that one point.
Don't take my comments as being a put down at all mate, just trying to save you walking the same wrong roads so many of us already have .... <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />
Andy