Take care about the angle of the rack arms. The Katu has its rack mounts pretty high up on the seat stays, which are already run higher than a lot of folding bikes. You can see in my photo that the rack arms are almost horizontal. For a rack sitting lower, like next to tire, you'd have to be able to bend the arms upward to meet the seat stay mounts, which may or may not be feasible, depending on the shape of the rack and the profile of the arms. If you do a Google image search on the Katu, it looks like all the photos with racks are of the standard, big-wheel type that sit higher.