Looks like APEX has A6 bipods and A6 stocks for sale. Do you need a special A6 booster in order to use the bipod, or can you just use a A4 "standard" booster? Does the bipod ring just get tightened against the barrel jacket, or go into some slot on the A6 booster? Thinking about getting a A6 stock/bipod set, I just do not want to change any other parts.