Purchasing the most advanced fishing line can be a sizeable investment.  Utilizing backing line when re-spooling your baitcasting reels can help make the most out of that purchase by saving anglers hard earned money in the process.  Backing line is any line that is put on the reel as filler to have the primary line go over the top of it.  As an example, say your reel holds 150 yds of 12 lb test. If you were to fill that…