I reckon the Tommyaxe has the most unexpectedly interesting stall of any aircraft I have flown.
It certainly does FTDK. You could never be sure quite which way it was going to go. It had a GAW1 type aerofoil (if memory serves me correct) and for consistant stall characteristics it was important that the airfoil section hold it's shape. For reasons best known to Piper, only every third wing rib was in fact a rib. The other two were simply L section skin stiffners.
This was different than the prototype which evidentally had a full set of ribs. The wing that went into production was known to be a 'soft' wing with the skins oil-canning under varying flight loads. This altered the shape of the airfoil section in different parts of the wing, hence the inconsistant stall beaviour. Piper also changed the ailerons and flaps (read, cheaper) to a more basic arrangment. A number of other changes were made to simplify production and to cut costs.
It was never quite the machine that Piper originally intended it to be.