A friend, who formerly competed in the unlimited category, quit doing snaps after watching the deflection of the horizontal stabilizer on his Extra 300 while snapping.I've been running loads on my aerobatic ultralight napkin sketch, and because the vertical stab/rudder extends above the tail the loads end up being higher on the top than the bottom (air loads). My worst case so far has been outside snap rolls which is probably a loading the aircraft being discussed won't see, don't know what the standard part 23 loadings are.
The other considerations are how the wings, wing struts, and landing gear attach. In many examples, the wide part (bottom of the triangular truss) helps with the torsional loads for minimal structural weight. Think of pinned spar attachments up top plus pinned strut attachments at the bottom, as well as the need of the landing gear to deal with side loads.I haven't considered landing loads, but they also put the top in compression, which is often the critical state for a truss. Makes me want to put the single pole on the bottom.
As usual, though, everything is a trade-off, but the “two on bottom, one on top” configuration appeals to me.