The 2GB limit is not a limitation of Installshield, but rather a limitation from the Windows Operating System which does not support CAB files larger than 2GB - therefore no compressed MSI file can be larger than 2GB.
The solution here is to build an uncompressed release as the cab files are no longer in the MSI file and therefore this limitation no longer applies.
It would be possible to create a compressed setup.exe, however there is also a Windows limitation of 4GB on a portable executable file.
