@roslof This reply is amazingly detailed, thank you for taking the time to write this up. End result: your instructions helped make everything work perfectly and I am now able to run the older versions of lr-mame. Thank you again!

@duglor

I don't understand what you're asking exactly. As I said... just set the control to 3DO Lightgun. That enables the 3DO Lightgun controller which is emulated via the mouse. It's not really any different from any other core.

The PSCX2 team has completely removed the plugin System in the newest version. They stated that they will readd the ability to rebind the controller via gui in later updates.

You could have kept the newest version of PCSX2 using the method i stated above.
But good that you have found a way to get the old version of PCSX2 so it works for you again.

Swapping out the cfg files did fix the problem. Thank you for that suggestion.

I'm not an expert in overvclocking, but if the same values have been working without issues, on the same PI, they should be ok with the new version.

@lurkout performance / familiarity. We don't use retroarch as a frontend, so there is less need for xmb. I'm quite happy leaving it with the boring old gui for now anyway - but users can switch if they want.