Spektrum Accessories Avian Backplate Motor Mount, 35-42mm

On the Horizon Hobby website page for the SPMXAMA1205, in the Questions section, a verifed reviwer (store owner) stated that "firewall mount holes are 42-48mm apart." Please asvise as to whether the SPMXAMA1205 firewall mount holes are 42-48mm apart, as the part description is "Avian Backplate Motor Mount, 35-42mm"

what is the distance between the two opposite motor mounting holes please?

Will this work with the Rimfire 42-50-800k ?