There are many options available to you.  I wouldn't recommend lowering your body fat any lower that your current 10%.  Because bones make up a significant part of human weight, I'd focus on them.  Individual bones can be removed (some without significant loss of functuality to the body.  Important work has also been accomplished in the area of hollowing of bones, which if you go crazy, you may be limiting yourself to a life in water.  The simplist way to lose bone mass would involve amputation, which would have the additional benefit of losing muscle, skin, and fluid (blood).  I hope this helps and good luck with your weight problem.