Ryano was right, using a loose shirt can really save the shoulders. Anytime I am having some issues, I throw on a regular katana that is about 3sizes to big and do a few sets.
Ram works great for my training partner. He has the double ram (the stronger one). It has been great to him. I am sure the slingshot works in a similar manner. I just dont like how the slingshot goes on the elbow. I think both claim to add about 10-185% over your raw max. Should allow you to train with a little heavier weight weekly.