For your purpose, it sounds like you want the clan tag to be 1234, so you always have the option to easily find the id, and do e.g. "sm_kick #1234 bye", etc.
OnClientPostAdminCheck isn't being re-called if people are changing their clan tags in the middle of the game, so I'd say this place may not be the best place for this purpose, at least not alone.
You can try adding something to block the clantag change, e.g.:
PHP Code:
public Action OnClientCommandKeyValues(int client, KeyValues kv)
{
char kvKey[256];
if (!kv.GetSectionName(kvKey, sizeof(kvKey))
return Plugin_Continue;
if (StrEqual(kvKey, "ClanTagChanged")) {
return Plugin_Handled;
}
return Plugin_Continue;
}
and then add your custom clantag just like you do in OnClientPostAdminCheck as well.
Or simply change it back above within the if returning Plugin_Handled, and eventually add further things such as admin exceptions, etc. if necessary.