Spider cracks can be normal, as a unit ages and stress differences between the gel coat and the underlying fiberglas. But probably not normal in a newer unit. Stress cracks are somewhat different, they originate near the edge of the cap and are due to screws being overtightened or that the entire cap is under stress and something has to give. Some pics would help.
Texas Baptist Men-Retiree Builders member since '01
13 Silverado 3500HD D/A, 2wd CCSB srw, custom RKI bed
11 Cruiser CF32MK