The right way to attach sprinkler to the supply line is with swing joints made with "funny pipe" and elbows. The makes the very adjustable, they will give is stepped on or run over, and you don't have to get exact pipe or nipple lengths. To install them now would be a bit of a chore, it would require digging up all the heads. You might want to do it piecemeal, doing just the ones that are really low. Not familiar with the Hunter heads but the trajectory may be a matter of adjustment. Do you get the spread you should? If so, don't worry about it.