There seems to be many bytes left! :)
$ zopfli -c st4k |wc
11 127 4050 $ zopfli -c st4k |wc
11 127 4050 $ curl -s http://danlec.com/st4k | gzip -cd | 7z a -si -tgzip -mx=9 compressed.gz
$ wc compressed.gz
14 84 4048 compressed.gz