well technically its 'instruction sheet', but its 3" high, forgot to measure the width (its 2:20 am and didnt turn the lights on when i checked). the panel is 5"x24-25" or so. if you look at the pictures with those numbers in mind, the width of the instruction sheet area is probably around 20 inches, counting the metal pieces holding the glass cover piece.
and now that i type that, gotta correct you in that neither thing is plexi. havent taken it apart in a while but i think the instruction sheet glass with held down by those 2 metal end pieces, held to the frame w/nuts.
the joystick panel is just 1/8" metal or so (maybe thinner) and buttons just clip on while sticks are mounted to plates underneath, im guessing your hori sticks are exactly the same (which looks like you might be familiar with already with swapped buttons on yours).
not so good picture of the inside of the blast city panel in my cab:
nice gratuitous mirror finish on it i wasnt expecting, my old astro panel was just flat metal with a large chunk of rust. different top finishes too.
anyways since youre using wood (and plexi?), you know how to mount the sanwa stuff in it? or are you gonna make your own metal panel perhaps?