Hi Tom. Sorry about the delay in answering but I was working away from home.

My Jack Daniels has a through neck and I cut the slots in the tin in a somewhat similar way to Uncle John and Bairfoot but on mine I bent the cut part in on each side of the neck (like 2 little wings), at each end of the tin, and screwed these (2 screws to each wing) to the neck (the lid is not screwed to the neck at all). I did not find the need to add any supporting blocks to the neck but some bracing will be necessary. The lid on mine is screwed to the tin all around the edge (17 screws - bling really) and I found it necessary to glue strips of wood aroud the edge of the tin for the screws to screw into otherwise the sides of the tin bent in. The lid will need some bracing as the tension of the strings will cause that to bend in - all I did was put a sound post between the underside of the bridge and the neck. Do take care cutting holes in the tin as it will be inclined to tear - sandwiching it between pieces of waste wood helps. I was pleased with the tone of the guitar but there's not much volume acoustically so if you want loud you'll need to use an amplifier - I used a piezo (in the same way as Uncle John) and a pre-amp. Hope  this all helps. If I can be of any further help - ask away.