Do you plan on having people sit at the ends? Is there a reason you don't want to do 3" tenons and have the table a couple inches shorter?
Grant, Thank you so much for your completely unhelpful comment. I'm not quite sure why you thought it necessary to reply at all honestly. Also, what exactly is wrong with attaching "functional" breadboards with loose tenon joinery? Are you of the belief that the breadboard MUST have a groove in it? If so, then you need to do your own homework. I've made many tables using loose tenons in the breadboard. One of those tables has been sitting in my mother's dining room for almost 15 years with zero issues.You do realize that this is not the way to attach functional breadboards right? Your table boards can still cup. If you re going through the trouble of building it do a little more homework and cut the ends properly