Hi,
Have you considered making xz-compressed source tarballs available in file browser (https://www.postgresql.org/ftp/source)?
The tarfile for v11rc1 compresses to 15.5MB (with -9) - nearly half the size of the gzip-compressed file that is currently on the browser.
Modern versions of tar will automatically decompress .tar.xz files with the usual "tar -xf <filename>" invocation.
Keep up the good work!
Steven.