I wanted to let all know the outcome of my consideration of a shoulder holster. It all started because I was considering carrying a G21 or occasionally a 1911. Both are pretty heavy and I considered a shoulder holster would be a bit easier to deal with.
A couple of things that influenced my decision were the shoulder holster, if horizontal, was pointing backwards and could be unsafe; also whether vertical or horizontal, I heard a lot of people who had worn one complain of the straps on the shoulders and "knowing the holster was always there." I guess it's like wearing suspenders: while some people like them, many do not. Additionally, one guy I spoke with mentioned that wearing a coat in Texas is a pretty short season (its around 65 degrees today).
It finally dawned on me that instead of finding the "perfect carry", I could actually carry two different guns based on the seasons. I decided to carry my G30sf and go with a Bianchi Black Widow - this is an OWB leather holster with a pretty good forward cant and very comfortable. I wear it at the 4 o'clock position under a winter vest. I also have the mag holder on the other side at 8 o'clock. The .45 is pretty much undisputed and the G30 carries 10+1, which should be enough to serve everyone that comes to the party. :biggrin: In summer I will stick with the G23 .40 with 13+1 of high performance defense ammo, and use an IWB that I am already used to. I also bought a very stiff Gould & Goodrich gun belt to wear with jeans and holds the Bianchi very well.
I thank everyone that posted to the thread. It opened up some factors I had not considered, and that is what is real good about this forum and all your comments.