Mast Rake
According to the North Tuning guide the Mast rake should be 6-7". It should not matter what type of backstay adjuster you have. Since you have a mast head rig you can not "bend" your mast to an appreciable extent using the backstay. What you can do is tighten the forestay with your backstay for the proper sail trim of the jib for the conditions.The prebend in the mast set up by the shrouds should also be set according to your sailmaker. The more bend the flater your sail and less power.Frank