Why not do what they are doing over in the CLS forums? New members first few (6-10) posts are moderated, and accepted/declined on that basis. After that moderation time is up, members can post when they want without thier posts being screened? I know that this is extra work for the moderaters, but maybe if all new posts are moved straight to the admin board, and have an accep/deline button that mods can press after reading it. After that it can be moved back to the forum it was 'posted' in...?
Only an Idea but it's been put into practice elsewhere.
Cheers,
Alex ;D