i used my live rock and sand to cycle my tank. it was the first thing i put in there. It is my understanding that if you add a lot of LR to your tank after the cycle, then it will go through another small cycle. Since you are in your cycle I would think that it should be fine to add it now. how much are you wanting to add? do you have any now? size of your tank?
How about adding LR into a tank that has been running for 5 months? Would I have to do a water change? Emperor Angel...I would take the damsels out because once you want to get rid of them, it'll be tough as heck. Trust me.
Add l/r slowly unless you are getting it fully cured and is being transported quickly from its site to your tank. In that case it can be added quickly, or right away as long as it is from a trusted sourse. I bought 50lbs of live rock recently from a reputable on line retailer. It arrived in good shape and there was definately some die off. I put about 20 lbs in my 125 and divided the rest amongst the other 3-55's. Everything went fine. NO amonia spike and a slight nitrate spike. Again it came from a trusted source. Good luck.