We have a GE Spacemaker Microwave installtion...

Question

The issues we're running into are that we have only located a single stud in the middle of the area we want to install the microwave in. The wall bracket shows holes on the sides so should we use dry wall anchors and would that be sufficient? Also the small cabinet above has a fiberboard in the recessed bottom so we're not sure that installing the bolts from the cabinet into the top of the microwave would offer any sort of support at all. What should we do? The model is a GE Spacemaker JVM1630WB if that matters