Hi. I have a 2016 Trek Superfly 9.6 (Hardtail). As I'm getting older, I would like to have a little assist going up hill. I thought getting a new electric mountain bike but can't since the cost of new one is out of reach. Is there a kit that I buy to convert my existing bike? With disc brakes, I'm guessing I'm limited to a mid drive? If so, any recommendations? Thanks in advance.