Has any body been able to crack the standard luggage rack by overloading it?

I was just doing a fiberglass repair on my luggage rack after an encounter
with a low garage
(it fits but just, however I forgot a small package up there & it compressed
& shattered the rack:)
But now its prolly way stronger (3 sheets of glass on the underside at
$4/yard why not) ...
then some short strand fibre glass on the exposed surface & then a coat of
tinted truck bed liner on top
looks brand new :)

But I notice that the tray in the rack still flexes before my re-enforements
it must of really flexed..
I am thinking of 1 more sheet but running some 3 pcs of 1x3 under that &
fibreglassing that in
like they do on boats to give it some ridgidity ... but this might be extra
work for no real gain
hence the question ..