Let's specify your needs.
Do you have small children aboard? If so, I don't think jack lines alone will be sufficient. What you may deisire more is basically an aft pulpit and life lines run from the aft pulpit to stanctions on each side mounted at about where the cabin starts. This creats sort of a barrier to help keep your children aboard. Not as foolproof as jack lines, but readily available and more convient than securing a strap. This will have great physcological benefits making sailing with children more comfortable. Also, make sure you install a ladder. Catalina Direct can sell you one and their technical department can probably provide fairly accurate placement measurements. Ladders are necessary for children and adults. And jack lines are also used on main sails, so if you get some pictures of a line attaching a main sail to a mast, don't be surprised.
