I have a six line and cleaner in my 12gal nano with no problems. It has almost been two years for that tank. I also have a CBS in my larger reef with two cleaners and have not had any problems. I am not sure I would attempt them both in a 29gal however. The CBS may need a bit more real-estate then that in order to get along with other shrimp.
Some people are like slinkies...they serve no real purpose yet can still bring a smile to your face when you push them down the stairs!:p
Have a great day! Brian