Alternate approach utilizing c# script when building plugin.
add this to your plugin.build.cs and then delete Binaries, Intermediate folders from your plugin directory and re-build the plugin.
//Fix slow HTTP download.
string txtPath = Path.GetFullPath(Path.Combine(Target.ProjectFile.Directory.ToString(), "Config", "DefaultEngine.ini"));
string fixLine = "\n[HTTP.Curl]\nBufferSize=524288\n[HTTP]\nHttpThreadActiveFrameTimeInSeconds=0.00001";
if(!(File.ReadAllText(txtPath).Contains(fixLine)))
{
File.AppendAllText(txtPath, fixLine);
}
So, if users download your plugin, it will run automatically when they build it before opening the project.
However, if they only enable the plugin and use auto restart, the configuration may not work the first time.