I was just about to say why that wouldn't work, but if I removed the wall mounting bracket and mounted a board to which i could re-affix the mounting bracket... that should bump it out perhaps just enough. The holes and vent in the cabinet above would need to be adjusted, but that shouldn't pose a problem.

Thank you for the idea, i just needed that fresh pair of eyes on the problem.

You're welcome, and in case this question occurs to you--I recently checked to see if the filler piece was sticky or grungy from the steam and grease, but my hood fan must be working well, because the filler isn't grungy. I mostly use the front burners, especially for sauteeing, so that probably helps.

You'll need to cover the bottom of the "filler" with a piece of metal, since it's over the range top.

Right.

Here's a link to another discussion of this issue with some photos...

OTR microwaves not compatible with Ikea Section depth