If you’re comfortable with Python, the magic for this happens in “RenderArgument()” function in “[repo]/plugins/Houdini/Houdini.py”. That’s where you’d need play with (if you’re not already).
How are things failing?
From a maintenance point of view, I’d put your eco wrap in a Windows batch file and use that in place of hython in the plugin config.
REM Run eco with needed flags
eco -t houdini16.5.323 -r 'hython %*'