Yep, tummy sleeper from day dot here.
Make sure they are on a firm flat surface not on blankets or pillows etc, elevate the mattress a little.
Charlotte always slept better longer and easier on her tummy. She was also a long skinny thing and had vey good neck control from very very early on. She was a natural tummy sleeper and afterthe first week I wasn't so anxious sleeping her like that.