Depends on what you're trying to do. Since I usually don't need 24v, I keep a jumper in my field box that I sometimes use to join two batteries together. More than once I've borrowed another flight box and used the jumper to connect from one power panel to the next in series.

If I was going to run 24v on a regular basis, I'd get a bit more creative with the wiring, and probably ditch the power panel all together.