Nah, bugger it, go into Kosmic in Osborne Park and tell them you have a winter project and want to make your own cabinet, could you run a tape over one. I would. I have made my own cabinet for my Fender "The Twin" and now it is
a piggyback model, much lighter and sounds sweeter.
I found that the measurements do not have to be exact to withing a millimetre, 5mm would be close enough as you can tune the cab.
Altronics, near the Perth rail station have the tubes(god, I can't think of the proper name) for that.
I have just made a couple of foldback cabinets using 18mm ply, don't use chip board it's shit. On reflection a finger jointer would have been fabulous for the box, I just glued and screwed a 40x20 strip in the sides.
Try this site
www.shavanomusiconline.com they have all sorts of projects and lots of graphics.
When you are done there and want to cover the cab. go to
www.partsexpress.com they have carpet for cabs or alternately go to
www.antiqueradiosupply.com and they have the tolex, it's a fraction of the cost what you pay in Australia, and more importantly a bloody site quicker from the US, 10 working days usually, compared with upwards of a month here and in Aus they charge like a wounded bull. Also look at their speaker costs, I am looking at some Eminence Patriots.
email me if you get stuck, not that I can do much 1800 km north of Perth.
Clive