Rav Nochum Eisenstein shlit”a (a godol from Yerushlayim who was originally a Rov in the United States and was one of the closest rabbonim to Rav Elyashev zt’l and frequently Rav Elyashev communicated messages through Rav Eisenstein), was on R. Dovid Lichtenstein’s (who gives a Lakewood shiur on current topics in halacha) radio show this past Wednesday night. The topic of halachic prenups came up to which Rav Eisenstein commented that “Rav Elyashiv was against any type of prenup” because of asmachta, that was a halachic opposition (that potentially renders a subsequent Get to be a Get Me’usa). He further commented that Rav Elyashiv also had a hashkafic opposition that they were “not the derech of yisrael sabbah… not the way kiddushin is done.”
Rav Eisenstein also said that he had an extensive discussion with Rav Dovid Feinstein shlit”a this past summer on various issues, and he is authorized to quote Rav Dovid that “Rav Moshe was against all prenuptuals” halachically and hashkafically.