In my woodworking experience I've had little contact with breadboard ends. I am now making a drop board for a desk and have milled the board with three tennons on each end that are 1 3/4" in depth (from left to right) and 2 1/2" in width (from front to back) They are 3/8" thick. I plan to use the pin tecnique to fasten the ends to the board. Keep in mind these tenons are spaced across the width of the drop board such that the middle tenon is on the center line of the board and the other two are spaced out toward its corners. Now, obviously, the purpose of the ends is to prevent the board (it's a 15" wide piece of wood) from cupping or warping. Should I glue the center tenon on each side and let the rest float?. The pegs in the outer tenons will pass through elongated holes in those tenons. Should these pegs be glued to the end board? Not to the tenon, of course.
The only time I've done this was some 30 years ago on this maple table. At the time I didn't own a router - much less a router table; so I didn't use mortise and tenons joinery, Yet the leaves have not warped and one can notice seasonal movement between the ends and the leaves.