I have done a lot of research and from what I gather, HQ in concentrations of 5-6% with 10-15% Lactic Acid in a GEL based formulation used in conjunction with Retin-A 0.1% gives effective and consistent lightening. I've been using RA/HQ 4% and it gives results but its a long road. Lactic Acid doesnt interfere with RA at low concentrations and it has great tyrosinase inhibiting properties and its moisturizing to work well with the RA. Unfortunately, I haven't found any source that sells HQ in 5-6% concentration in a GEL base with Lactic Acid, so its up to me to compound it. I would gladly appreciate your advice or recommendations on where to go to compound or share effective home compounding recipes.