Matt,
This is what I do in games where there are no foul lines, especially if I'm working solo:
Pre-game plate conference:
Me: Okay fellas, today I am by myself. Your league has decided that one umpire is enough, so that's the way it's going to be. You do not have foul lines drawn (many times I have NO foul lines whatsoever) past first base, so whatever I call is what it's going to be. I will have no argument of fair or foul on balls hit past 1st and 3rd. I'm not entertaining arguments on safe/out calls on stolen bases. I'm going to give it my best look, and if the ball beats the runner and a tag is down, that runner is going to be out. Any questions?
Them: No sir, Mr. Umpire. . . . .
then they argue and whine anyway, and I immediately remind them that if they want it called differently to pay for 2 umpires (or chalk the field, whichever is applicable). After this one reminder, I start ejecting.
I also don't invite the new head honcho to further discuss
anything.