Just FYI, I calculated R for my pink phantom leds the same way, and they came out way too bright. Like blinding. You might not want to calculate with maximum current. I might suggest using 10mA or even less. Since resistors are cheap, you might order several values, and then test them before you solder them in. I think 220 and 330 are commonly recommended for the higher voltage leds. I have seen many people use much higher R values too.
FWIW, I also recommend soldering the resistors and diodes on the bottom of the PCB instead of the top so that if you need to remove them, you won't have to desolder the whole board to get to them. Then you can either desolder or cut the legs from the bottom without having to remove all the switches to take the plate off. WFD recommends this in his instructional youtube video for phantom assembly (very helpful by the way), and I found it VERY helpful when I realized my leds were way too bright and I wanted to change the resistor values.