Jake, what if the distance between the 2 points is more than twice as long as one of the strings? A 4th patch?

In other words my snuffer measurement is 6' 10".
I located the 2 points as you said. 1 at bottom between the clew & tack and 1 from the head. The distance between the 2 points is 16'.

Is a 4th patch necessary or will a middle patch do the job?

This is a spinnaker for a Bimare 18HT - 34' mast.

Thanks for your help!