Create a second list where users post. It will have no PRIME-TIME and will have ACK=YES The first list will only allow subscribers of the second list enabled to post; the first list will continue to have PRIME-TIME enabled.
There is probably a little more to flesh out, but that's the basic idea e.g., who is authorized to post and with which SET options.
/Pete Weiss
@NIH '67-'69 -- can you say IBM 360/50?