Fiberglass leafs are similar to torsion bars in that seemingly small and insignificant chips can cause stress risers that lead to failures. If you avoid the chips that create the failure point, then you should not need to have visibility to the hairline fractures that would evolve form the chip. However, if by chance they do begin to split, I would think, based on pictures I have seen, that it would tear a rubberized coating far enough to be visible. Perhaps the compromise here would be to use this coating on the bottom and outboard side of the spring to provide rock chip protection, but leave the top and inboard side exposed to view for splintering.
Typically, most composite leafs are used in competition applications where they receive regular inspections. Even with this, most manufacturers suggest using something to protect the springs, usually suggesting duct tape.
The flip side is that GM has used composite leafs in Corvettes for decades. However, their transverse loction high up in the chassis provides and measure of protection compared to the mopar style, low and outboard in the debris path kicked up from the front tires. I have heard that GM Astro vans also used composite springs and they have experienced failures. I have no first hand info on that and no idea of any failures were because of the spring material or damage. FWIW, even if used extensively during the warm summer months, most of our E bodies won't see near the mileage in ten years that some one was heaping on a utility van in a single year.
