I wanna build my copy of 1x12 Marshall box 1931 B for my greenback (G12H -T 1217 from 1972) i. I have my first greenback (also G12H -T 1217 from 1972) installed into 1x12 1931 A box and sounds great. I wanna have two 1x12 boxes. It is great for versatility (small gigs only one box, bigger gix both boxes). Do you have any typs, about measurment, material, thickness of walls? I have 8 mm plywood (to front I would buy 15 mm plywood)? Do you think it could be enough thick? I measured on my original 1931A box thickness 13 mm everywhere + cca 2 mm tolex. And how about grill? Also, 1931 box has a plank across the speaker in front (it serves for holding Marshall logo - I am thinking if to copy even this or if it will perhaps sound better without this). I am not sure what is the material in front, it is taugher material than on fender amps. Amp that I use is Marshall PA20 from 1972. Thanks for any advices.