Thanks. The stock Horizon cable is about 1 meter, and 1.5 or 2 would be enough.
Horizon needs USB 3 to use the high speed imaging. The Pegasus Ultimate Powerbox is supposed to be a powered USB3 hub, but the Horizon either hates the Pegasus, or hates the cable I used to connect the Pegasus. If I was stuck with USB2, I would just use my 490ex instead. Really if you are not using USB3, you are missing out on a lot of the benefit of the fast download times. It makes alignment and focusing very fast and convenient.
Fortunately I can just run a second cable for the Horizon USB3 using through-the-mount cabling. I also use Hyperstar that puts the camera on the front end of my telescope, so I need a lot of extra play in the length.
I actually do use a NUC, but its in a box under the tripod. The 1 meter cable is fine when the camera is attached traditionally, but not quite long enough for Hyperstar. I have thought about just mounting the NUC to the OTA as Pegasus has a bracket for it. I guess if I don't find a cable that makes me happy, this is what I will do.