We are considering continuing our drive from Tolmin to Piran, without backtracking. We would drive through Kanal, Solkan, and Stanjel, skirting Nova Gorica. (Not leaving Slovenia.) We would appreciate opinions from fellow travelers who did this, as well as those who decided not to take this route. Hvala lepa!
This is the route I took in reverse from Piran to the Tolmin area and up to Kobarid. Easy drive. Went fine.
We just drove Piran to Kobarid on June 13 and it was fine/easy. My one comment for your planning: I wish I'd booked a tour in Stanjel via their TIC. I tried, but contacted them too late. Otherwise the wandering on our own felt a bit meaningless, and motivation to wander was also tricky due to jet lag and the heat/sun. :)