Hey buddy
Nice ride!!! looks like my bike when I take off haha
I use both front and rear of this motor with the GM 48v battery. Fully charged its 54V and this yields around 40km/h probably more like 37/38 with just running 1 motor and standard other wheel.
Unfortunately the only way you will get a greater top speed is by upgrading your battery to a 48v considering you are using the internal controller.
I would not suggest going faster than 30km/h on your bike anyway as those types are really only designed for 20-30km/h but you have a nice helmet should anything go wrong!
What you have is probably perfect for the build type, and you will have better range with your battery (16Ah) too. But if you really want that extra max 10km/h more you will have to upgrade your battery....