I really don't understand you how you could loose him, just keep him in visual contact, if you do that you won't loose him.
Remember to trim to keep the forward speed as close to his as possible, then just turn at his turning points. If your far enough back you should be able to see him make a full turn before you have to, and thus you can make sure you keep behind him. If you leave it long enough that he has completed his turn you can then just cut the corner, keeping him either in your left/right and centre window at all times.
Remember to not do too much to the collective when your turning, or you may end up a lot higher/lower than him and loose him that way.
EDIT: This is all a lot easier if your using a HOTAS and some sort of head track software, as you can look around far quicker, basically glancing in directions, which means your eyes off target time is limited as much as possible.