The channel for my Alu Extrusion bottoms out ~6mm, for 1/4" panels (that don’t compress like soft Ply), I’d consider M3 x 12mm with 1/4" panel instead of recessing the holes. Although recessed bolts/holes do look nice.
Only used 1/8" and 1/16" polycarbonate panels for my double panel build. IIRC price jumps up significantly for thicker stock. Curious to see how your 1/4" turns out, I still haven’t made a front door/panel to help fully enclose.
Went with Polycarbonate instead of acrylic after Brent mentioned microcracks forming if exposed to IPA when cleaning the bed. Hoping Polycarbonate is more resilient?
Backup of the 250mm panels used for my build are at v1engineering-mods/mp3dp-v4/mods/panels at main · aaronse/v1engineering-mods · GitHub. However, I would probably build differently if I was to start over… Saw bunch of great builds at RMRRF with panels that quick release compressing clips, with some gasket/foam tapes stuck to the frames. Easy access to front and back would be nice, even if the side panels were fixed.