A solution that worked for me was to export the configuration file, make a backup copy, then edit it manually with a text editor. Just look for the MAC Address of the device, then you can set the parameters you like and reload the config file. Below is the config for one of my entries:
(10
(visible_to_dns(1))
(ip(192.168.1.211))
(hostname(elevendottwo))
(start_time(1228410561))
(end_time(1228496961))
(uid)
(hardware_mac(00:0c:29:bc:eb:0c))
(is_dynamic(0))
(valid_time(1))
(is_ms_null_terminated(0))
(is_abandoned(0))
(stability(2))
(is_ever_acked(1))
(is_hostname_fixed(0))
(vendor_id)
(is_detected(0))
(display
(client_type(default))
)
)
Did I mention you should back up the file before making any changes? ;)
Good luck,
Tyler