I am using IS Express.
I find the final setup.exe generated by IS Express is not compressed very well.
I try to recompress setup.exe(6086kb) with WinZip default settings, the compressed file size is 5434 kb
I try to use WinRAR(Best compression), the result is 5368kb.
So there seems to be a lot of spaces that can be compressed.
So I follow the instructions in https://docs.flexera.com/isxhelp25/isxhelp25.htm#helplibrary/SettingsXML-Compress.htm#gettingstarted... to set the compression level to 9.
Then I recreate the setup.exe file. But find its size is reduce by 100bytes only.