We have longish runs between bike and car in a hack setup.
Also note that you need to count total circuit length, including distance to ground. For instance, if your device is 3 feet from battery, total distance is 6 feet.
One of the things I'm [probably for no reason] worrying about is the extra load we put on a bike's wire when we tap into it to feed a circuit on the hack. That is, if we tap into the bike tail light wire to feed the tail light on the hack, will we over-stress the bike's wire? I have no idea how much safety margin is built into the bike's wiring, especially on a canbus system.
It is better to have ridden and crashed, than to have never ridden at all.