Hi Nick,

The short answer is yes you can do this, no new ECUs are needed. You could even run them together now, but with the latest optimized acceleration setting (firmware), they will run together in a twin better.

As for the A123 mod, I am sure your 4.xx version needs a new power circuit board, and I am 95% sure the 5.xx will need it as well (the older boards cannot be modified).

This is US$90 per ECU, and the software update is included, and the 4.9 will get a new hard case as well.

What are you putting it in? I have a twin on the board but I don't think I will get to it until I get my youngest through college (she is 2)

Regards,