I spent some time modifying a rear hub motor to fit a 110mm front fork so I could add another motor to the front. Instead of buying a larger rear motor I decided to do this and just add another 35$ controller. I was only looking to increase the torque and acceleration,top speed is already fast enough. So by adding another motor to the front I have basically doubled the torque output and increased the weight by around 13lbs. I already had a battery capable of 100 plus amps and 3.7kw so plenty of power to supply two 35-50 amp controllers.
This thing is way more fun than anything else I have built. It's basically a small powerful mini electric motorcycle that is comfortable to ride and just goes for ever. The pictures don't really do it justice, I will take it out and try and get some better shots. It's pretty dope and I am wondering why a company hasn't done something similar. Keeping the bulk of the weight in the base makes more sense than putting it up high.