I wear a shoulder rig at times. And one of the things with a shoulder rig is that it be balanced in weight, if it takes several mags or one mag and a light, or in my case another pistol. I've found that it weighs more but I'm less tired and feel less muscle discomfort when the load is balanced some what. I adjust mine up higher and I have less problems with the rig wanting to shift. Wide shoulder straps are your friend. With a good rig adjusted to fit close you can wear it over a tee shirt and use most any shirt as a cover. I've used silk shirts plenty of times as a cover, you just have to be aware of the breeze and hold you elbows in a little when entering or exiting a building at times. This picture was taken before the final adjustment. I wear it higher than that.
