"We're going to stay in extra night in Rovinj instead of trying to force a night in Venice. Challenges to the plan always welcome."

I'm with kja - What time is your flight out of Venice? Most (not all but most) flights to the States leave early AM - some VERY early.

Sounds okay, although I too feel more comfortable being in my departure city the night before.

Alternatively you could reverse it and travel Venice - Rovinj - Koper - Bovec - Ljubljana - Venice. Or Venice - Rovinj - Ljubljana - Bovec - Nova Gorica - Venice.

Have you checked whether there are hire companies in Bovec? Do ferries run every day between Venice and Rovinj (they didn’t when we travelled but that was years ago).

I feel like you will be skipping past so many great places but understand that you have limited time and have made choices.