Is it permissible for a husband to stipulate to his wife that they refer to your preponderant opinions when disagreeing on a religious ruling? Is this considered extremism? And is there a connection between avoiding doubtful matters and choosing the preponderant over the less preponderant?

There is no harm for a couple to agree, upon marriage, to refer any disputes to a specific scholar or a recognized fatwa-issuing body, in order to act upon what that scholar or body deems preponderant among the sayings of scholars, provided that the couple are followers [of a specific school of thought] and that the reference body is the most trustworthy in their view. The relationship between avoiding doubtful matters and choosing the preponderant opinion depends on the preponderant opinion itself. If the preponderant opinion is the stricter or more cautious, it aligns with avoiding doubtful matters. If it is the easier, it differs from it. Avoiding doubtful matters is achieved through piety and acting on the more cautious approach, whereas determining the preponderant opinion is based on the availability of evidence and the principles of jurisprudence. Acting upon the preponderant opinion is obligatory, while caution and piety are recommended if they contradict the preponderant opinion.