After reading Jamo's thread, I started hard mewing again.
One thing I'm worried about - when I push hard with my tongue, my digastric muscle (the one directly behind the chin) gets worked out a lot, which gives me a double chin.
Am I doing it wrong? Or is this a natural part of the process?
Thanks to Jamo who recommended hard mewing while in McKenzie chin tuck, which does lessen this effect. Open to hearing alternate opinions as well!