THE ACFT WAS REPORTEDLY STALLED ABOUT 30 FT ABOVE THE RWY AND A HARD LDG WAS MADE. THE MULTI-ENG RATED PLT WAS PRACTICING SHORT-FIELD LDGS UNDER THE INSTRUCTION OF A CFI IN PREPARATION FOR OBTAINING COMMERCIAL CERTIFICATE. THE ACFT WINGS AND FUSELAGE SUSTAINED STRUCTURAL DAMAGE. THE PLT REPORTED THAT THE CFI URGED HIM TO GO SLOWER THAN HE FELT WAS PRUDENT AND HE RELUCTANTLY COMPLIED. HE INDICATED THAT HE WAS FLYING THE ACFT BASED ON AIRSPEED INDICATIONS IN MPH. THE CFI REPORTED THAT HE TOLD THE PLT TO SLOW THE ACFT TO 76 KTS AND THAT HE BELIEVED THE PLT REDUCED THE SPEED TO 76 MPH. THE AIRSPEED INDICATOR REPORTEDLY INDICATED IN BOTH KTS AND MPH. THE CFI REPORTEDLY HAD 37 HRS TOTAL FLT TIME IN THIS MAKE & MODEL. AN FAA INSPECTOR REPORTED THAT THE ACFT STALL WARNING SYSTEM WAS INOPERATIVE AND THAT THE PLT, WHO WAS ALSO THE ACFT OWNER, WAS AWARE OF IT. NEITHER THE CFI NOR PLT REPORTED THE ACCIDENT; THE FAA LATER LEARNED OF THE ACCIDENT FROM A 3RD PARTY.