They will not fit properly in the stock location as they are bigger then Sub-C. But A123 will be releasing a smaller pack that will fit. If you get the FLM chassis that Mike carries, then A123 cells will fit. Look at the 2 pictures below and you'll see that they won't fit properly.
This is two 3s1p packs
This is two 2s1p packs
6 KiloWatt A123 Racer
GTP-Pletty Big Maxximum+RX8. GTP-C50-6L Hacker+RX8. CRT.5-Pro4+ZTW esc.
24s2p EVG SX 49.6mph Ebike.
18s4p Raptor 60mph Ebike. 11.5KW