The only time I saw a backward evaporator like that was in Cuttingsville VT. The guy switched his pans around like that and even had a homemade piggyback over the firebox end of the rig. His claim was that he could make darker syrup that way because the syrup in the syrup pans boiled slower and allowed it to darken more. His market was mostly for dark amber and B. I don't know why else you would set it up that way.
How big is the model?
Sugarbush in Tunbridge VT.
930 taps for 2013 (made 483 gallons)
2hp liquid ring vac
3x10 small bros w/preheater, blower and new airtight front = 140 gph
Sap Brother Eco-50 RO(got 180gph @250psi in 2012)