Re: Where can I find cab designs and handles?
m'kay... pictures are worth many a word..
This is a 2x15inch fender showman cab. It's split, mostly i guess for extra strength, no essential, especially if your cab is a little less long.
Pine planks all round, except for the baffle (in which mr speaker is bolted)
Notice how if you took the baffle off, both sides would essentially be the same. The little strip of square woods create a nice home into which the baffle seats, likewise the back cover. Notice however that the baffle is screwed in via the interior, leaving the grille cloth nice. Notice too how the grille cloth is peeping in. It is stapled to the edge. Notice too that the baffle is secured with lotsa screws. Finally, see how the rear cover's screwholes are equally plentiful, even into the centre room-splitter.
Sealed and ready to rock
And next, as you might not have the machine/option to finger joint the corners, i'd say your wood guy can make a nice strong glue n square-dowel inside-to-screw-into substitute. As long as its strong, which it will be cause he makes kitchens. Maybe he'll use round dowels and round holes?
Notice how the cab isn't super deep. This makes it somewhat practicle, and sounds great. But the maths guys would shriek in horror, just like the archtop guys shrieked when fender put strings on a plank of cheap wood.
Finally.... don't stress tooo much about the baffle material and thickness. These famous blackface amps, they used chipboard baffles! But nice thickish ply, is an upgrade. Ads a bit more control/tightness to the sound, as the speaker has a nice stiff anchor off which to push. The mounted only on the edges is good, if done properly, and i'd imagine then just one speaker should be involved? Not sure.
In a sentence... Just copy Leo Fender, can't go wrong...
As for the speaker holes, measure thrice, cut once!
However, understand the strong points and weaknesses of sealed vs open cabs. Show your carpenter these pics, and the only thing to fear is that he might be insulted for being asked to build something so basic!