Wood processors pay premiums for stable and stiff timber, while forest growers often prefer to have fast growing trees as to shorten rotation lengths increasing profitability. The preferences are not always aligned, particularly within wood properties. Stiffness, used for grading logs, is positively correlated with growth-strain with a correlation of 0.61, an unfavourable correlation requiring a trade-off between the two traits. While zero growth-strain is desirable to be economically viable to process, some unknown maximum value below which little economic loss is experienced exists. Stiffness is already used for log grades, structural timber in New Zealand requires 8 GPa \cite{b2005}. To meet these stiffness grades at age two, some compromise with the level of growth-strain in the stems is needed.

All stems measured within each family were averaged to give correlations between properties at the family level (Table \ref{960788}). A very strong positive relationship is evident between growth-strain and stiffness at the family level. This means that reducing growth-strain will require reducing wood stiffness at the population level. On the positive side, some Eucalyptus species have such high wood stiffness that a reduction would not have practical implications from a wood processing viewpoint.