I've cut the hole for the lower battery box in the boot. I'm going to have a sheet metal box folded up to fit and I'll spot welded in place (well, I'll spot mig weld it). I used string lines to get the box square, but unfortunately got one corner wrong, so I can't take the cut out part to the sheet metal guy as a template. I'll have to trace it out with cardboard. I plan to fit 28 cells in this box and a bunch more above them.
In other news, I talked to F40 Engineering at the New Zealand Speed Show. I showed them some photos and they are enthusiastic about joining my motor to my gearbox. This is an improvement over my previous engineer who wasn't. I'm going down with the parts on Tuesday.