I don't know much about Mantak's overall system but I do know that any exercise has the potential to go wrong even the very basic ones. I guess he made the descision when he put some of the more advanced work that people would do it in the correct order.

I see the sexual practices as possibly being similar to other exercises. For example weight lifting for your bicep etc in a gym. One should first have an instructor or read a book about it so you learn about reps and sets and how to take things step by step in order to get to higher weights etc. With the sexual practices you are using more delicate anatomy so if you launch into it not heeding the many warnings then it is from a result of your own ignorance to your own bodies feeling. I'm not saying people who have been injured did it this way but I bet a few of those saying that they have been fall under this category.

I think the long term "injury" of supressing sexuality or over taxing sexuality and orgasm/ejaculation is worse than the few out there who have had injuries which they've learnt from and taken a different course all together. If one has thin or weaker vas deferans for example and they have found out that they can't do the finger lock during a regular ejaculation then it is a lesson learned. One could then do the sexual practices of not going over the edge which isn't harmful and if they happen to go over the edge then what's the big deal if you ejaculate once?

Again supressing or over induldging in sexuality is more harmful than the alternative.

If one authors work doesn't agree with you there are others in the field such as Margot Anand, Charles and Caroline Muir etc This new area of western sacred sexuality is a fascinating one I feel. We are seeing the blending of a few traditions from China and India s well as western magickal schools.