I'm new to LEM/SolarWind (2 days old to be precise) so my answer may be riddled bad practices... In any case, like you, I just discovered that SoftwareInstall event's are primarily MSI events and was not in the least bit satisified ... Here's the rule that I've created to filter out exe installs... as you can see, it will need to be fine-tuned to your environment.
All it does is display all process starts/stops that are not standard windows processes which start in Program Files, Windows, or the short-hand PROGRA~ directories. Hope it works for you
