Happ usually has mounting intrsuctions on the same page with its products. Those should give you what you need.
Only semi-related advice:
Theres a BYOAC member, name of Ponyboy, who sells happ's entire line at an awesome discount. You can find him in the Buy/Sell/Trade board. Another bonus to buying from him is that hes much friendlier than Happ is, atleast in my experience.. bet you could get an answer from him if Happ doesnt have the instructions posted.