custom fiberglass box question

I have done fiberglass trunks in the past but every time I have done them I used either an mdf box surrounded by fiberglass or half fiberglass and half mdf boxes.  Im currently designing a custom trunk for a customer and I want to make a sub box out of just fiberglass.  How many layers of fiberglass would any of you fellow installers use to ensure stability and sound quality?  Thanks ya'll for the input!

Is there a reason it needs to be completely fiberglass ?

Hey HottAccord, whered you get ur interior done ?

I agree with the push test its nifty, if your box can't hold up to ur thumb has it gunna hold up to all that pressure.

stand on it if it flexes at all do more glass

if they flex, they will distort, so yes they need to be as sturdy as sealed boxes, unless you want to either fry a couple amps or puke a bunch of subs.  Don't put all of your weight at once on the box before you make sure it won't flex, gradually put weight on one foot until your other foot isn't touching the ground.