This is where it gets complicated. BMSB do not have ideal controllers for the Q128C. The S12SN at 40 amps is way too much. I'm 12 1/4 stone and use a 14 amp 48v controller, which gives plenty of power for steep hills, and we have a lot of very steep hills around here. The only suitable controller that BMSB do is the 20A one for the Dolphin battery, which you have to blank-off to use on its own, i.e. remove the battery connector and cover or plug the hole:
https://bmsbattery.com/controller/698-sine-wave-controller-for-09-case-controller.html?search_query=20a+sine+wave&results=95
When you use that controller, all the connectors are moulded and the cables are too long, so you have to find a way of losing/hiding the excess wire, which is why I prefer the box type with normal connectors, which I put in an under-seat tool-bag.
You can get the aluminium box type controllers from here. The 17A one will probably be ideal:
http://www.pswpower.com/peng/pic.asp?ModID=PicS224&TypID=S220052
The 201 rpm Q128c does about 19 mph and the 328 rpm one does 28 mph. make sure that you chose the one you want.
You also need a pair of the BMSB torque arms, though you only need to fit one on one side.
As far as I'm concerned, the 48v Q128C and a KT sine wave controller is ebiking nirvana. The motor will be so smooth and silent that sometimes you think you're providing the power yourself.