RE: PX III Track Tensioners
I see "budget" in your list, but honestly, consider simply buying the complete PZIII Asiatam lower hull.
I don't think anyone has any complaints about it, it's metal everything, and is complete.
I started down the path you did, and ended up taking quite the beating when I sold all the brand new, uninstalled "metal upgrade parts" I had assembled. I was simply unhappy with the wavy, flexy HL hull, and there was no realistic workaround for that. Not to mention torsion bar suspension, etc.
Along comes the Asiatam metal hull assembly. Had that been out when I first started, I would have saved myself $$.
Just my opinion. Good luck!