I'd like to put a Campy Centaur rear Long on a 29 cassette with a compact 39/52. Any issues or is a medium cage preferable?
Either a Long 90mm or medium 75mm would work just fine. The old racing triple was a medium cage and I ran it on my XC bike with no problems. The rear cassette was a 13-29 and the triple was 26/40/50. I ran a 30/42/53 front crankset as well on another bike with a medium cage Daytona. The long cage would be ok as well. I am running a touring setup with a 28/40/50 and an 11-34 rear cassette SRAM with the long cage. I have tried a 20/42/53 on that setup as well with no problems. If you stay within the campy recommendations you will be safe. Branfordbike is a great source.