You would want to be supported to at least the point that the bottom of the engrave is above the 1.5" off the bottom under the crumb tray. you might want to try this ;
No matter what, you do not want to cut or engrave anything more than 1/2" off the deck of the crumb tray or 2" above the bottom under the crumb tray.
Beyond that, not all woods are equal and some will not cut or engrave much more than 1/4" thick material.