This project is called Jew Piss Star.
Sorry, but you can't unhear it.
So Jupystar is pronounced like Jupistar.
Jupis, like lupis.
People try to be too clever with these portmanteaus, and end up with either something unfortunate or unpronouncable.
That's what I said. But differs to what you said before. /Jupi/ has only one stress; your previously mentioned pronunciation requires two, also two s rather one that exists in the word.
I'm sorry, but I can barely hear it in the first place. The lexical stress in Jupystar is entirely different to what you're claiming.
Jupystar must therefore be pronounced like Jupistar.