The yose controller will just stop applying power to the motor beyond 15.5 mph, it wont hamper you beyond the mass burden pedalling any faster, so if you could pre conversion you can again post

. And with motor assist to get you upto and at 15.5 mph you should have more energy to devote to top end spinning.
Ive crossed paths with plenty of folk who would take pleasure in spotting and reporting a 'suspicious' 20 mph ebike, and if you haven't im pleased for you.
yose-power employment of either julet connectors or the smt automotive style connectors is basically the generic industry standard that all ebike controllers employ.. the odd brand may add their own twist to monopolise spares resales? and bafang/higo connectors can muddy the waters if unaware, and while there are a couple of known gotcha's NONE apply to yose-kits afaik so rest easy on that score..
Topbikekit can even sell you a 48v kt controller that fits inside a hailong battery base, if you buy one? I for one would lurve to know if its a dual voltage capable 36v/48v device or just 48v as the site description is a bit ambiguous.
- the more compact space than within the 'silver box' format, could limit circuitry options??
Making an ebike travel at 20 mph isnt difficult, the question to ask yourself is however is it a wise thing to do?
And if traversing areas unpopulated perhaps it is but on the same roads day in day out?? -
Perhaps if your the most courteous and polite fast ebike on the road givng NO-ONE any cause to raise an eyebrow you will be ok??..