20% sacycilc acid ? sp?

I am going to do a chemical peel on some areas of my pride and joy and I am worried if this acid is okay. Does anyone have experience with this stuff? I am in another country, not a western country where common wart remover can be found. I only found 20 % sacycilc acid. I have heard and read about 17% on this site. Is the 20% going to make a drastic difference in the outcome of the application compared to the regular 17%? Any suggestions on how to apply 20%? I have some serious dark spots from clamping that are just plan unsightly and I need to get rid of them before my cock is seen by another women again. Who has used 20% and what was your experience? Thank you so much for your feedback.