I put the controller on my 2019 Rad Rover. Between 7 and 10 mph, the stock Bafang would buzz like a LOUD, angry bee and the entire frame would vibrate. I tried every C5 and C14 combo to no avail. An email reply from Bolton said their controller would make more noise because of the increased output of the controller. With their upgraded motor, that wouldn't be a problem.
Long story short, I switched back to the stock Rad controller and display, and all is quiet again. From everything I've read, the Bolton Upgrade Kit is a great upgrade. Unfortunately, it just wasn't, for me.