A lot of the play I enjoy the most is right on the edge of safety. I do a very thorough job of researching what I am contemplating asking my wife to do to me. This is much easier nowadays what with the web and computers and search engines.
In the old days, I started by checking with BDSM magazines such as Drummer and SandMutopian Guardian. I also knew many people with similar interests I could write (real letters) and find out about their results.
For example, I wanted huge amounts of saline injected directly into my testicles. Drummer had an article which strongly suggested not doing this. They also had a number of men who said it was not nearly as dangerous as it sounds. I contacted some of them. One, the most useful, said that he did his play partners with 50 cc of sterile saline per testicle frequently and none of them had any problems. He gave me names and addresses for several. I corresponded with all of them and found out that they had no problems from this procedure and the amount injected.
Dear wife and I finally did this after I had convinced myself that the risks were within the level I was comfortable with. When she started injecting the saline into my testicle, the pain was incredible. We went slowly and I managed to take the full 50 cc in each ball. Now, I love having my balls hurt and abused, so this was something I was most happy with.
When we finished, my balls were rock hard as they were so inflated inside the membranes that encase them. As the saline was absorbed the pain went down and the next morning I was basically back to normal. I experienced no difficulty.
Do I suggest doing this? No way! Most men will say that is way too risky and they are probably right. One error and the patient could have serious problems leading to surgery.
Each of us must determine the risks of any particular activity. Then we must determine if we want to accept the risks involved. That is called informing oneself. It is the major part of playing safely.
Speed