I presently have 12 Xbee 900Hp Pro modules and with Network discovery back-off (NT) set to 13 seconds, it will miss 1 or 2 modules in it's discovery about 1 out of every 5 times I issue the ND command. I have to change NT to 30 seconds to reliable get them all. Is this time reasonable? I may very shortly be moving to 50+ 900HP's. Should I then have to further increase NT? All parameters are at default but NI,NT and API.