Mag and SD gun in the same pocket does not work for me.
I would think that the above rig might work better if the gun was set lower. I see the same problem with the Milt Sparks design. Gun sits high.
I prefer maximal slide coverage for a few reasons. I think that a Hedley back pocket holster is a good compromise, if you would call it that, for both the front and the back pocket. But if you're going to carry a extra mag, then it has to be on the weak side.
Just my 2 cents.