I've seen the Bob Allen ones worn with the included strap, and they did work well. As CZ said, they are a bit thicker though. I believe that the Reactor pads come with a mesh pocket that can be sewn into a garment. I think if you were to put the thicker Bob Allen one underneath something with a thicker or more firm fabric, you gun mount wouldn't suffer at all. You would only have to contend with a longer lenght of pull for you mount.
I hope this helps,
Karl