Tangoll, neither of us should double post, but since you started
Otherwise there are a number of shoulder straps that might work in your favor. According to the reviews, this (
http://www.upstrap-pro.com/) is the one most photographers (porters of really heavy gear) swear by.
The Briggs Riley strap is excellent, as is the Tenba strap. I own both. Actually, since I bought the BR BB107 I am the lucky owner of two BR straps.
The BR strap is flexible, has a decent anti-slpi padding and has a double concave pad that adapts to the shoulder very well thus providing a good fit.
The Tenba strap on the other hand only has a single concave side but it has more padding towards the exterior to compensate for the slope of the shoulder. The anti-slip material is also very good. Besides that it is the most "Macho-Man" looking strap I know off.
Op-tech straps can also be had with anti-slip lining and have a nice flexibility to them.
http://www.optechusa.com/product/det...&CATEGORY_ID=4
Of course, the easiest and most effective is to simply carry the bag cross-strapped over the torso. No special strap needed, best weight loading, best against theft, easiest on the shoulder pads of your suits.
If you don't want to wear the strap across the torso make it short so that the bag rides on your hip. You should be able to use the bag as an armrest for the arm that holds the bag. This is a very comfortable position and the weight of the arm will actually give just the right pressure on the strap at the shoulder that it won't slip. Having the bag's top sit lower than your belt line will result in the worst slip and worst load for your back and shoulder.
You need to find the right length where the strap is short enough so the center of the bag sits right at your hip bone but that it is still long enough that you can wear it across the chest if needed. Usually this adjustment means that when you cross-strap the bag will be in the ideal position to sit in the hollow of your back. This is the best position for carrying a heavy load.
Till