The improvements are greater with the u=s instantiations, since with sentences it's more common for more than one CF to be realized in the same grammatical position; for example, in the IS instantiations in which PRO2s are considered as realizations of CFs, we find that 5.7% of utterances (38/669) have more than one CB.
strong C1 is already verified with these instantiations, even with simple grammatical function.