I've gone through the mod install guide 4+ times after freshly installing Ps: T, and everything works, except for stackable rings - which is unfortunate as it's one of the most important ones to being able to enjoy the game.

A mod update to remedy this would be very appreciated.

Really? Which version of the mod are you using? I'm currently using 4.12 and it's working fine for me. Check your SETUP-PST-TWEAK.DEBUG file (should be created in your root game directory) and search for "rings" and see what it says - maybe something isn't copying over correctly?

Though since it copies stuff into the same general places as most other tweaks (at least from that pack), it seems weird that they're not working when everything else is...