The best way to prevent damage in fiberglass kayaks is to transport them on the side, due to their better structure this way.
Easy on and off the rook rack.
Easy to tie down.
Good straps acompany the system.
If the user READS the instructions and has a bit of tie-up common sense, there's NO WAY this rack will fail!
NOTE: for long trips on rough roads (twice I traveled 5.000+ miles with my fiberglass sea kayak), it is best to add another layer of foam at the bottom, where most of the weight of the kayak sits, to prevent a cosmetic damage to the gel coat.