Hat for Tefillah – Da`as HaMB
The MB in Siman 91 s`k 12 states that one must daven with a `big` hat (and not merely a Kuppel) since this is the way one would stand before`Gedoilim`.
I have investigated and it is a fact that one would not approach nowadays any royal with a hat – it therefore would seem this MB is not le`dina anymore.
It could well be there are additional inyonim or reasons for wearing hats which the MB does not mention but it seems this will be categorised as `chumrahs` and not ikkar ha`din
Does the Rov shlit`a agreee to this?
Yes, today one without a hat can still be considered dressed respectfully and is not violating halacha by davening without a hat. See Tzitz Eliezer Vol. 13 Siman 13, Vol. 14 Siman 49.
Sorry for the delay as the Rav has been abroad for an extended stay.