Tiki 21+ uses the last version (3.0.6) and that works fine. I've just updated one of our shopping sites here to add international shipping with a tracker, a plugin
Oh, and please do improve the documentation where you see it isn't good enough rather than just complain about it - as you know, Tiki relies on volunteers to help!
Thanks, maybe this will help. Please be so kind, since you have managed to make this run, to distill all what you had to modify into the Tiki code. Strip it of all that is only relevant to your site, generalize things etc.
Especially regarding Paypal. Paypals documentation is abundant. Unfortunately the error message the sandbox spits out isn't, so it would be hard to find out why the sandbox no longer works (I assume that at some point in time it did).
With respect to improving Tiki documentation, in order to do so I would have to reverse engineer the code... How could I document software I haven't written?