  We have investigated the efficacy of two recently proposed variations of the
pair-natural-orbital approach to reducing the scaling of coupled cluster
property calculations. In particular, we have extended our implementations of
the PNO++ and combined PNO++ methods, which make use of field-aware
pair-densities to define the virtual-orbital spaces used to describe electron
correlation effects, in order to test their accuracy, efficiency, and
robustness on larger molecular systems than previously investigated. For
fluoroalkane chains up to 1-fluoroheptane we find that the PNO++ and combined
PNO++ methods yield smaller localization errors in response properties than PNO
for similarly compact virtual spaces, and, while the PNO method performs better
than the PNO++ method for correlation energies, the combined PNO++ method
recovers similar accuracy for correlation energies to the PNO method. For more
three-dimensional molecular structures such as $\alpha$- and $\beta-$pinenes,
the PNO, PNO++, and combined PNO++ methods all yield similar errors for
response properties, whereas for ($S$)-1-phenylethanol, the PNO method performs
slightly better than the other two approaches. We also investigate the use of a
product density to define the virtual space, as well as two candidates for
defining weak-pair contributions.
