Yet another update. The Alien Gear Tuck IWB holster just arrived today.
I gotta be honest. This will take some getting used to. What I really think it will require is a couple of inches of my waistline...

Where I can fasten a given pair of pants now, the addition of the IWB and holstered P320 adds just enough to make it difficult (if not impossible) to fasten my pants...

Ugghh.
I like that I can adjust the positioning of the clips on it and will probably do so. I did get the metal clips (since It will, more than likely be on my Uncle Mike's EDC belt), but I'll have to flush down inside when I put the belt on. But, yes, the gun holsters much better than the supplied OWB holster from SIG Sauer.
Time to get on that Elliptical again!