Kind of a pun on words... heart strings, heart springs, for the abstract valentine stained glass pattern.  The border has rounded corners, and thus might be best in a wooden frame made custom, or perhaps if you make this large enough, you can use a zinc bender to make the corners and make the zinc seam on TWO points.  This would be like an L with a curvey corner, at the top and in the bend,  and one made a mirror image, joining the two pieces of zinc before the curve on alternate sides of each side..... At least this is what I would try.  The alternative is to make this small and use the easy to bend u chanel zinc.