It's probably hard for most people to understand this but, to me, the use of 3% peroxide is way too limiting. As I understand it, it takes 2 or 3 days or, whatever, for the HCl/H2O2 or H2SO4/H2O2 to do the job. If you always use 3%, you'll never be able to do it faster. That would drive me nuts, knowing that there's stronger stuff out there that might speed things up 4 or 5 times. If you had something stronger, you would be the master of the situation, rather than giving that distinction to the peroxide. You could adjust it to almost any speed you wanted, within much wider limits.
I noticed on the web that Clairol makes a 12% hydrogen peroxide that is sold in beauty supply stores.