Sewing - back pack zipper repair

My back pack has been in the sewing room for quite awhile waiting for a new zipper!!  I had repaired the teeth several times but after a few repairs the teeth were too thick for the mechansim to go over them and it did not allow the zipper to close at the top.  Not effective!! So today I dug out the bin of zippers to see if I had one that could replace it.  I found several with double zipper and I choose this one with silver tabs.  I decided not to try to undo the zipper - the fabric is very thin and I expected it would be difficult to get the new one in with precision.  So I decided to see if I could remove the teeth of the zipper without damaging the fabric of the zipper.  I had stitched the teeth back into place previously so I concluded that there would be some sort of stitching that attached the teeth to the fabric.  Yes, there was and so  I used a blade and remove the teeth from the fabric of the zipper by gently cutting a few stitches at a time all the way along both sides.  Once the stitching was cut I was able to pull on the teeth to remove them.  You can see the "teeth" above - just a long length of very strong plastic which formed the teeth.  The other photo shows the intact fabric on each side of the zipper still in place.  I simply placed the new zipper inside and started stitching as I spread the fabric of the old zipper apart to accommodate the new one.  I did have to do a bit of hand stitching in both ends to secure the new zipper to the fabric of the old one but that was easy and now the backpack is back to being secure with a double zipper!!  We bought them from Lee Valley many years ago and I have used this one a lot so I will now be able to use it again when I go walking, kayaking, etc.  I have been "borrowing" Brian since mine was in need of repair.  Therese