MOTM

Well, another, more convoluted/MOTM solution is to have 4 pieces: two side
rails
and 2 top/bottom rails.

The side rails are like 2 inches long. They have slots, so you can "wiggle"
in the vertical
direction (actually, either top or bottom needs to wiggle, the other can be
fixed).

Rather than butt the MOTM panels up against the wood sides, a small filler
panel could
be used. This would allow more room for possible tilt/lock mechanism.

The issue is the (in this example) "floating" top rail. If you were off say
0.080", then you could
drive screws into the top, not having the 'L' touch the wood. Certainly, it
wouldn't go anywhere,
and the screws would keep bowing and flexing to a minimum.

But, I think this gap is "ugly", compared to Moog's wood peeking out along
the top edge.

I think this requires more thought, at a later date. Bigger fish to fry, as
Grandma said.

Paul S.