I am installing an OTR microwave between cabinets which are 15 1/4" deep. The OTR needs cabinets no more than 13" deep, so I've built out from the wall 2 1/4" using a stack of three 1x6 boards. This is along the lines of the answer presented here. The bumpout is attached to 3 studs using GRK RSS structural screws (5/16, 5 1/8" long).
For now, I have attached the OTRs metal mounting bracket/rail to the bumpout using five 1/4 2" long lag screws, as in the picture attached. These screws do not go into the studs, but are secure in the bumpout. Is this sufficient for a ~50 lbs. OTR microwave? Or should I have the rail directly attached to at least one stud, too?
Thank you in advance!