Not knowing how to post pictures I'll try to describe the Lazy Jacks on our Allied 39. We're on the 3rd or 4th iteration over 39 years. True, you need to keep the "halyard" from banging the mast. We took the halyard from the small turning block high on the mast back about 2' to a cleat on the boom. It is both halyard and 1st lazy jack. Your drawing above shows such a cleat.
The halyard is long enough to let out when we raise the main or want to put up the awning which goes almost to the mast. A figure 8 holds the bitter end in an eye strap and shock cord holds the rest of the lazy jacks to the boom in a modified "L".