You probably need to allow more than 4 or 5 per day to encourage your readers to submit stories. I would suggest putting featured stories at the top and other

You probably need to allow more than 4 or 5 per day to encourage your readers to submit stories. I would suggest putting featured stories at the top and other noteworthy submissions below or on anther page. People really like to see their names in lights. Some concession to that will encourage that. Of course the downside is more trash. HN survives by the diligence of its community. Manual moderation should work well too.