All 747 models have electrically signalled, pneumatically powered LE devices with electrical motor back up. Is not a similar combination of inboard krugers and outboard slats used on the 727 and 737? The Convair 880M also used the same kruger/slat combination. The 747 differed only in that it used variable camber LE devices in the mid and outboard positions instead of slats and used pneumatics for normal operation. Presumably stall characteristics drove the decision to use krugers inboard on all these models.