You're going to get a lot of duplicates, since every map release from Slipseer will allllmost certainly then show up on Quaddicted.
It would be nice for the backend here to compare the zipfile names to catch duplicates, but I _think_ it's impossible to get the zipfile name from Slipseer just from page-scraping. Hmm.
FWIW you could fetch headers on a Slipseer download link and look for the content-disposition header, e.g.:
> curl -s --head https://www.slipseer.com/index.php?resources/cold-light.170/download
| grep -i content-disposition
content-disposition: attachment; filename="coldlight_1_2.zip"