If cutting deep, like it sounds like you will be doing, be sure to do it in several passes with the last being just a final light cut.
I once needed to make raised panels for exterior shutters and could not buy a bit that would leave a wide enough tenon along the edges of the panel, because a molding needed to surround the panel and both needed to fit into the dado. I ended up not only removing the bearing from the stock bit, but also grinding off the pin that the bearing had been attached to. This modification allowed me to make the raised panels the way that I needed to, but there was no way to re-install the bearing. The fence position is now the only way to set the cutting depth with that bit. I hated modifying this $100 bit, but the job justified it, and covered the cost of the bit.
Central North Carolina