You,
“Rav Aharon states (MRA, 6:10) that that the MB maintains that the majority of Rishonim do not accept shishim ribo, and therefore, Rav Aharon argues the heter is mefulash umechavanim ”
However, he does agree that according to the MB’s understanding of the Rambam (as per Magid Mishnah etc) we would at least be “m’tzarif” the shitas ‘Rabanon’ of ‘Lo Asi Rabim um’Vatlin Mechtzos” to the shitos of Shishim Ribo.
The only issue he has is with the GR”A, and on the same note, the Demasek Eliezer on the Biur haGr”a (364) is definitely NOT like R”A on the issue of mefulash.