The Limits of a Chumrah

It is well known that many non-observant Jews do a sale that is absolutely invalid. Their food purveying businesses may not be patronized until the chometz from before Pesach is presumed to have been sold.
Many people take this even further and—like the Gra, zt”l, —are unwilling to use even chomatz that they are certain was sold in good faith. Yet even though Rav Shlomo Zalman Auerbach, zt”l, was also careful regarding this chumrah, he also set clear boundaries as to how far it extends.
Some students in Kol Torah asked Rav Shlomo Zalman permission to go home for Shabbos. The reason they gave was that they were careful not to use flour ground before Pesach even if it had been sold.
To their surprise, Rav Shlomo Zalman refused since he held that this was an unnecessary stringency. It’s not as if there was any evidence that the flour had been chometzdik before Pesach, so it was clear to him that there was no halachic reason to take this chumrah so far.
Those who do not rely on heter mechiras chometz after Pesach are often in a quandary regarding when the production is from new flour so that they would be permitted to purchase different items. Certain important rabbonim urged Rav Shlomo Zalman to join them in pressuring the va’adei hakashrus to publicize the dates that various products were finally produced from flour that was not sold for Pesach.
Although Rav Shlomo Zalman himself observed this chumrah, he refused to have any part of this. “On the contrary, I don’t want to put my name to anything that would implicitly invalidate the sale of chometz, since the geonim of earlier times relied on the sale after Pesach.
“Let those who wish to be stringent in this matter find out the dates themselves!”