With the motor in its final location, it's time to look at battery placement for real. After cutting the carpet from the cargo area, it became obvious where the limits would be (you can see the spot welds of the frame rails to the floor pan). It also became obvious that my original 3x3 layout will not fit in the area allocated, so it's time for an asymmetrical layout that matches the available space. In addition, looking more closely under the rear seat, it is clear that only two batteries will fit here. Four batteries are not possible without cutting the frame rail, which is an incredibly bad idea.
So, here is a test fit with actual batteries in the rear. The five batteries near the seat back are in their final position - a box will be built to contain them. The three batteries behind those five will join six others sunk into the floor of the cargo area. A box will be built to contain them as well:
In the front, the motor mounting provides a challenge for laying the batteries out as I had originally planned. Instead, I'll go with three groups of three, with the last battery replacing the large starter battery (a smaller aux battery will go on the driver's side, along with the DC-DC converter). Here is a test fit of the three groups of three - the box in the lower right corner is the same volume as three of my batteries.
Due to space constraints, there will not be a box completely enclosing the front batteries. Instead, there will just be racks supporting it, along with a plastic top / hold-down for each group of three (and the solo battery) to prevent the batteries from flying around and to prevent fingers from accidentally brushing up against 312-volt power.
The good news is, even with two-by-fours and 3/4 inch plywood in the way, the trunk still closes with the batteries in the above position, so I think that this design will work:
So, here is the new component layout. The controller still goes in the front, above a group of three batteries. Two more groups of three are in the front, along with a solo replacing the large starting battery. Two batteries are under the rear seat, and fourteen are in the rear cargo area (9 of which will be sunk below the floor level):
Business travel and vacation will interrupt progress for a couple of weeks; when I return, it will be time to start fabricating racks and boxes!