gobucks - whatever you do, don’t overtighten the shower screen and dispersion plate. If you do, crazy thing happen. Water gets trapped behind the gasket when under pressure. The symptoms are the portafilter becoming rather stiff to lock in, and, if you use your fingers and squeeze the gasket, water squirts out.
You want to tighten the screw only up to the point the OEM stops rotating on the dispersion plate. If you can rotate the shower screen with your fingers, it’s too lose.
As for the IMS shower screen… I had it, I didn’t like it, and personally I don’t think it’s a good fit for the Elizabeth. It’s actually a La Cimballi shower screen.