Flatstoppers plus Chocks?

Hi all, I've parked my Charger on flatstoppers for the winter, and I was wondering if I also need chocks, too?

There's a slight incline to the garage floor, but I don't know if I should be concerned about rolling if I leave her in gear with the brake off, sitting on flatstoppers.

Put a piece of 2x4 behind one wheel and call it a day (or season).