My wife loves her Sam Andrews Monarch. Here are some pics:
In this one it appears to be riding high on her shoulders (low on her neck, so to speak), but usually the "Monarch" attachment point is lower.
Consider calling Sam and talking to him about your questions. He's a grand fella.
http://www.andrewsleather.com/
Here's Null's site:
http://www.klnullholsters.com/
And here are some more shoulder rig resources:
http://www.parkcitiestactical.com/shr.htm
Lima also has some great words of wisdom about shoulder rigs!