Perhaps if the T slots were made into L slots to eliminate half of the overhang (a L can fully constrain the joint) and instead of making the T-slot and the ‘tongue’ go all the way around just have it in two places 180 degrees apart (diametral length TBD) you could get it to print if it were laying on its side? Perhaps even adding a feature where the male T (or L) section tapers into the main body at each end…