Thickness /Strengnth question

Which is the best for strength . 2 layers of 3.5 mill glass or 1 layer of 7 mill.? I’m looking for the lightest and most strength.
Zane

Try making a small test panel as what is strong to one fellow, is weak to another.

But, more the layers (at 0, 90, -45 & + 45 degrees) will be stronger and lighter in weight.