First, that assumes 4 V/cell, but the nominal voltage is 3.75 V/cell, so the first-generation Chevy Volt modules are nominally 22.5 V (6S 3P) and 45 V (12S 3P), resulting in 135 V nominal (and up to 148 V max)...Can you just do one 144v pack in the front? (All in series).
Then do another 144v pack in the rear. (All in series)
and just parrallel the two packs?
The complete pack has two small modules and seven large ones, so this scheme would use all but one large module of the pack, which makes good sense to me (if the arrangement of two strings is desired).