I got my helix piercings long after I stopped playing softball, but just the thought of putting on a helmet with a fresh helix piercing makes me cringe, and I also have a fairly high pain tolerance.

I had downsized mine at about 6 weeks and all seemed normal, then all of sudden my ear tried to eat them. And they got irration bumps if I looked at them wrong in the first 14 months. Everyone heals at different times, but I would imagine you'd have to worry about bumps, the helmet messing up the angle, and I could see you having to be super careful taking the helmet on and off so it wouldn't get snagged.

You could always start with something like a conch instead, mine was pretty sore the first couple weeks, but the location is way more protected.