Minimum Jockey Box Coil Length

I may be coming in to some (relatively) cheap copper tubing. Does anyone have any experience as to what the minimum length of tubing should be used in a jockey box?

It seems a lot of people say to use 50', but it seems most of them are using SS coils, and I'm figuring copper conducts heat so much better, that 25' may be adequate. But, I don't want to cut it, and find out that it's not long enough.

The only info on jocky boxes I have comes from this site. Jockey Boxes Portable Keg Cooler Beer Dispensing Systems | BeverageFactory.com

They sell 50', 70' and 120'. More is better.

Sorry, I am not much help.

Remember with the coils that water will find its own level. You can pack the coils with ice but as the ice melts the length of tubing that is cooling the beer will decrease. There are solutions to mitigate this, like filling the cooler with water, but that's a basic principal to keep in mind.

However, I bought a 5 pass one of these: 7 Circut Aluminum Cold Plate for Homebrew or Soda - eBay (item 110289664729 end time Sep-21-08 17:56:36 PDT)

My lead on the copper went bad, so the cold plate may be the way to go. What did you mean by "5 pass"? Did you run lines in and out of the cold plate so the beer went through it several times before being dispensed to be sure it was cold, or is there some way of telling how many passes the internal lines make through the cold plate make before exiting? The ones I've seen on EBay just say how many circuits they have, not how many passes each circuit makes.

circuits=passes. a 4 pass cold plate has 4 ins and 4 outs so you can serve 4 beers