We don't know yet, but if you think it through, Regant(from which Gaderaza is based on,) only has two, and was able to use it quite effectively. however, Reborns Gundam managed to use the twin drive system against 00 better than Susuanoo and Regant using only one drive each, so most likely they have logically begun some research into the twin drive system. or perhaps even something else. 0 Gundam's and Seraphrim's GN Drive were both destroyed, but who says parts were not left over? Applying some of these surviving parts to a GNT Drive would produce some odd combination.