Original Xbox Controller padhack

I managed to snag a Pelican original Xbox controller from a goodwill for $1 today and would like to do a padhack and make it into an arcade stick.

I've done a couple padhacks, but I'm not an expert on the subject.

Here's the pcb of the controller I plan to use.



Am I correct in thinking this is a common ground pcb, meaning I just need to solder a single ground point and then daisy chain all inputs to that single ground point?

I also notice that the buttons all seem to have circles (test points?) in addition to the normal button traces. Can I solder directly to those circles for the inputs?

I don't plan to use the triggers, just the dpad, Back Start ABXY and Black and White.

Thanks for any assistance!