If your chains are to long simply twist them til you get the correct slack taken out,also they are supposed to be crossed to form a basket if it comes undone.

 

Don't see why you'd need two links per side. Just leave the old chain attached and buy new chain the length you need. Connect the two with a link, done.

As for the guys dragging chains that are too long, you can use a bungee cord to tighten it up and keep it off the ground. If the chain is ever actually needed, the bungee will just stretch or break and the chain will do it's job. If the chain is grinding down the road, it might not.