Reply by Lee Barker

What is the width across the grain?

And could you elaborate on this please: (quote) “The two sides are fixed and glued to the frame”

If I faced this problem, I’d go along with Oluf’s plan but in addition I’d use a router to waste out a center section behind the glass to, in effect, weaken the resistance to the flattening force the frame rails will exert.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"