If they are that insistent that R-net will do a dual 120 amps, would they be willing to sell it to you on the condition that if it doesn't deliver then you can send it back? If we weren't talking about wheelchairs, that would be a TOTALLY reasonable proposition! You're selling me a grade 8 screw and it fails at half the rated tension? Returned! You're selling me a gallon of milk that only has a quart inside? Returned!
Another serious option to consider is the Curtis enAble40 system:
http://curtisinstruments.com/index.cfm? ... y&catID=10They list 36.0 volts as being the highest point that you can set the battery meter, so I presume that the system can survive 36 volts, even though the "maximum motor volts" is maxed out at 28 volts. The most powerful system they make is 70 amps, which of course they tell me is per-motor simultaneous, 140 amps from the battery. If I'm right about P&G's rating scheme, this would make their top system stronger than R-net's top, but less than DX2's.
I also found their sales engineers to be friendly and helpful, and willing to guide me to a distributor (of golf cart parts!) that sold the OEM level PC programmer.