@BobKamman   The other 2/3 IS still a redwood tree, standing tall on its roots, perhaps trying to grow back the 1/3 and then some in the next 40 years...

As for my client's own redwood trees, HOA's consulting arborist said one could trim (top cutting) only up to 20% of each.

Do NOT mean to be UPLing (UPL = unlawful practice of law), but client told me his insurance company told him his next-door neighbor's insurance would NOT pay for the damages unless my client (i.e. as the neighbor's neighbor) had documentation showing he (client) had informed them (client's neighbor) of the danger of the trees and requested trimming and so forth at least FOUR times before the 1/3 tree's visit...   Different from my original concept of insurance.  I just sent my next-door neighbor the second notice about his trees.  Remind me here to send the third next week.