Thanks for the added details.

If you are going to add a mud flap to the rear fender I would strongly recommend reinforcing the fender attachment somehow. This is how I did it, and I am not too pleased with the way it looks but I think it is effective. Maybe you could come up with something that would look neater.



The Mobiky's rear fender is a weak point. It is not long enough to work well, but if you used a much longer fender or a long mud flap it would be too close to the ground when the bike is folded. And I rate the quality of the rear fender attachment bracket even worse than the Joy Tech front hub. I have seen pictures of at least a couple of them that broke off. With the weight of a mud flap added I would expect it to break much sooner. The front fender bracket is much better because it attaches to both the front and back of the fork crown.