issue is see with a moto is that you cant hear anything.
You can always drill a 1/4" hole in each side, where the ears reside.
(With head REMOVED from helmet!!!)
It doesn't change the structural stability of the helmet, whatsoever!
...
I have a friend that works for Snell.
Snell is the company that test's 90% of the helmets you can buy.
When you buy a helmet, it will probably say, "Snell certified" on the back.
This means, that my buddy, or one of 2 other people, tested and approved it first.
They do Shock, Pressure, and Destructive Tolerence testing.
DT is the funnest to watch.... Blast shield, and all.
...
Anyways, I drilled a helmet, and had them pressure and shock test it.
It still passed within manufacturer tolerences.
"Manufacturer tolerences", means your neck or skull will crack before the helmet does.
So ear-holes are a viable option.... At least w/ Fox helmets.
*
If you drill ear-holes, you have to glue a small piece of pantyhose, or fine screen,
over the inside of the holes.
Keeps the dust out.
Probably common sense,
but like my daddy used to say, "Common sense, ain't all that common no more."
EDIT:
Don't
EVER put a "BELL" helmet on your child...
I can't say why, but I
can say that I would NEVER use one.
Ever.