I am very familiar with shoulder holsters. In fact, my boss looked the other way when I was carrying (I worked in 'finance' and the hunting of derelicts). Whether or not the Miami Classic was as good as guys said--I think they just like watching 'Miami Vice'--that holster was hot item for more than a year.
My problem was having to wear some form of coat all of the time, and it gets steamy hot in Wisconsin. When I found a simple holster--no thumb break or a security strap of any kind--I bought a snub revolver in .38 SPL and pretended I was well armed.
Fortunately I got a better job and my new boss changed my job description to include concealed carry. I also got the job of being his wife's chauffeur. I still have a similar holster, it rides high enough on my right kidney for concealment, but low enough so I don't have wrench out my shoulder.
BTW, that .38 SPL provision is a very good idea for a body guard. If you shoot at all most times it will be indoors--and take it from me, your hearing will be gone for several hours. A magnum round might seem really sexy, but a 158 grain lead bullet is plenty loud, and will probably perforate the aggressor.