OK, so I have to go to Seoul on business and my company will pay for C class tix. I would like to stopover for a couple of days in HNL on the way back. Will pay the difference in airfare, if any, out of my pocket.

We have to use this lame ITN booking engine that doesn't give you access to the fare rules so I am struggling. If I use a stopover of more than 24 hours it downgrades me to Y on the HNL-LAX-PHL segments. I thought most business class fares allowed free or cheap stopovers. Is it true that you only get F seats on the domestic flights if they are connecting to/from an international segment that day without stopovers? Is there a booking strategy I should use so I get to fly domestic F both ways and get a low cost stopover in HNL?

TIA for any advice.