The FAA TCDS for the Stearman says
Empty Weight CoG: (-1.5) to (+0.5) solo from either seat
(-4.4) to (+0.5) placard in front cockpit: "Solo from rear seat only."
When empty weight C.G. falls within this range, computation of critical fore and aft C.G. positions is unnecessary.
So where you can sit when solo depends upon where the empty CoG lies.
There is that word "solo" again. In TCT's book it means two up I guess.