My Trailer has cradles and they have cracked lengthways (fore to aft direction) a few times. I believe they are being broken by passers by who try to sit or stand on them when my car and trailer sit in the parking lot while I am out sailing.
The last time I repaired the crack, I stitched it with long strand spectra core from a piece of rope. Then I saturated with epoxy and covered with woven glass.
Here is a link to a few pictures of my sloppy but strong repair.
Sewing up a cradle like the lacing on a football's skin. GARY