The online.paf installer fails to install when internet connection is slow. So these types of installers should give user a option to download the needed file using external download manager by displaying the download link when it fails to download the file. Then user can place the downloaded file next to the paf installer and run it again to install.
How slow a connection is it failing for? It uses the Windows internal internet APIs, so it should work for any connection, even dialup.
Sometimes, the impossible can become possible, if you're awesome!
Less then 10 kbps.
The problem with slow internet connection and online.paf Installer is that it requires very long time to download the files from the internet during this long time period any internet disconnection or power cut fails the whole process. And also sometimes the original download files removed from the server as discussed here - https://portableapps.com/node/39709
so knowing which file to download and the download url user can manually search and download the file using a external download manager with download resume support.