The Dreaded Inner Border Calculations

Here is another of the 6 projects from the gift box of scraps.  It looks a lot like another Pineapple Quilt I already have - probably because the fabrics came from the same LQS, just via different avenues.  Border is next - I had to use my own stash for the green border squares, and have run out but have another close match.   Hey, it IS a scrap quilt.  

I taught a class once about blocks on point and diagonal measurements and the 1.414 multiplication factor, and a couple of the gals asked "why do we need to know that"?  These squares on point is why you need to know that.  I kept the size of the border square same size and value of the block center.  A neighbor's husband was looking at quilt of mine that had a clever border and I heard him say to his wife, "Look what she did!" and ever since then, his kind comment has encouraged me to try a little harder on borders.    

Now I am facing forgetfulness for calculating the size of inner border when one has the center quilt top done and the outer border done, and how does one figure size of inner border(s) between them.   Ya can't jes go chopping off those squares on point, ya know!  The best instruction for me was from Gyleen X. Fitzgerald - but I don't remember them - must dig around my DVDs and relearn it.  She says, "Take out your brain and put it on the shelf, then follow these instructions, and don't think about it."   8-))) 

You can kinda see what the corner SHOULD look like.  The existing white border needs widening or removal.