I bit the bullet and made a risa fem plate model. I did use the YLT to design the top of a concrete vault years ago and I recall being amazed at how simple and efficient the method is. It really felt like engineering magic. I'll have to check this model with it. Thanks BA. I wasn't able to load an image, but I was able to create a slotted hole, and yes it did need a doubler plate. I experimented with plates perpendicular to the web, but the doubler had the most effect in reducing the stress around the hole.
I'm still surprised there isn't a table with published values for this situation.