Since you mentioned the model being a 26HE I'm guessing you have a Vista. I'm surprised the microwave was able to commit suicide unless it's mounted totally differently than the one in our 2013 Adventurer.
Our adventurer has a standard mounting plate affixed to the wall. 2 long screws pass through the microwave housing from the bottom at a 45* angle and anchor in the wall plate. There's also a bracket the width of the microwave screwed to the top about midway front to rear. This bracket has a vertical flange which is also screwed a structural member above the microwave. In total there are at least 6 screws holding the back plate to the wall and another 6 holding the bracket to the structural member above the microwave.
The screws holding the back plate to the wall are 3/4" long self tapping sheet metal screws. They are anchored to rectangular aluminum structural elements in the wall. The screws holding the top bracket in place are pan head wood screws anchored in the cabinet structure.
Hikerdogs
2013 Winnebago Adventurer