It wouldn't be a fixed lateral support though if you were to put a bolt through that last hole. Each side of the shackle can still move independantly of the other. Here's the shackle that I use, and recommend to everyone (not just because i sell them... but because they are, by far, the most heavy duty shackle available for the S-Series):

 

or you could get a set from http://www.3leaffab.com/