I have the same intuition. I think Underwood will give them a chance to be on the floor together, but unless one or both can hit short jumpers, it won't be effective against BIG level teams. On top of that, I see Payne as mostly coming in for Kofi, so now you're risking fouls on a potentially critical need late in the game. Rotations will be about who finishes, not who starts. And I think you're going to want your absolute best 5 for the last 5 minutes, which means they'll structure rotations to support that (i.e. Kofi should stay around 27 mpg again this season, and Payne will have to play the 5 more if there's foul trouble). Payne will get some minutes at the 4, but he won't solidify that unless he shows well there. I personally am thinking Hawkins makes incremental improvement this year, getting more minutes, but not expecting starter level. Hard to say how the 4 is divided up.
This is such a deep team, that I see a lot of experiments and evolution as the season goes on. There's a lot potential for different line-ups with this much talent available.