i was wondering this myself,as i chose a spot to weld the bracket to my frame.
so i got it in the spot where the adjuster was right at the bottom,and one link difference in length didnt work as far as adjustment.
i had to relocate my engine a little to make up for me needing a 1/2 link.
i dont really think there is a perfect formula,but i think the straighter the chain lower run is ,the less stress is applied for starting.think thats one reason i was having issues before.
60 miles and all is behaving like it should.
the adjuster should be in a spot where it will take up one link of chain.