Bill Tindall, E.TN
>Did you have a tenon? M&T with shoulder, which is critical to stiffness

Did you have one bolt crossing through a tenon and into another's end grain? no

I just did this exact same job (only one bolt per joint) and I wasn't all that impressed with the stiffness of the joint. I have made several beds with this joint including a loft bed with nearly 5' long legs. Also bunk beds and they too were rigid It was completely rigid. When the M&T shoulder is drawn up to the leg it can't move, any.

What kind of wood did you use? cherry