I dont put quite as much relevance on weighting as most people - whilst it very important for seo etc. In real terms.. you see adverts for cars at the cinema and adverts for perfume during the news. many of the most interesting things you find online are not those you are actually looking for.. IF you want real relevance put the latest 20 submissions as a feed to your homepage. wont interest that many but will increase submissions and will be very relevant.