Flat head & no helmet?

Any mommies out there that decided not to have their baby use a helmet for flat head and their head turned out just fine?

With my first child, he favored his right more and his left had more of a flat spot. However, we opted out of getting him a helmet. It's barely noticeable now with his thick hair 😁 Our new LO is 4.5 months and tends to favor his left side. He doesn't like to be put down during naps 😣 so holding him sideways (how he likes it) has contributed to some of the flatness 😟 I've been trying to do more tummy time, holding him upright most of the day, and switching his head from side to side during sleep at night, though he ends up turning his head left again or just flat. Anybody use any special pillows to help prevent or treat the flat head? I can't remember, but does the baby's head usually round out on it's own later on? I know the helmet can be pricey too if not covered by insurance...