Having played thursday social cricket and been hit in the head without a helmet i can tell you even at that pace it still hurts and can do a lot of damage - i managed to top edge it into my face - luckily i had turned to square leg to see where it was going so it hit me just above the right eyebrow. dread to think what would have happened had it hit somewhere else.I'm 38 and never had to wear a helmet through junior cricket but wear it all the time now - its a recent masuri so not adjustable grille - my only issue is that it tends to wobble about on my head when playing shots and running so i have to adjust it regularly.
Would using the chin cup not help with this? Read in another thread you tend to cut this off.