Back in the early 1980's Ross Baker created the Heron MJ1, a car very few people both inside and outside of New Zealand will have heard of, however it's distinguishing feature was the all fibreglass monocoque reinforced with a stainless steel mesh in the highly loaded regions. All up weighed 860 Kg.
It worked really well as he developed the technology making orchard spraying machines with a similar construction.
Attachment:
Heron MJ1.jpg
I don't know what type of stainless mesh he used but the regions marked blue in the plans (online at the local museum of technology, MOTAT) just state "including mesh", it was the '80's afterall.
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Heron MJ1 plans.jpg
https://heroncars.org.nz/heron_mj1.htmlIt worked really well for the chassis, Ross said that he never experienced any reliability issues with any of the 24 vehicles made. I don't know about rock impacts but would expect that the load will be distributed a lot better than without, although permanent damage may still occur. Sounds like an ideal candidate for a test panel that then gets subjected to a chipping hammer blow.