DRG ARR, THE ACFT (RYAN FLT 103) CRASHED SHORT OF RWY 3. THE FUSELAGE STAYED INTACT DRG IMPACT, BUT THE BELLY STRUCTURE WAS COMPRESSED & VERTICAL DECELERATION FORCES EXCEEDED THE DESIGN CAPABILITY OF THE SEATS. RESCUE PSNL HAD DIFFICULTY SHUTTING OFF THE ACFT'S ELEC PWR WHICH DELAYED REMOVAL OF THE 1ST OFFICER (F/O) FM THE ACFT. AN INV REVEALED THE ACFT WAS LOADED WITH APRX 600 LBS MORE CARGO THAN THE F/O HAD REQUESTED. THE CENTER-OF-GRAVITY (CG) WAS 8 TO 11 INCHES BEHINDTHE ALLOWABLE AFT LIMIT & THE FLT CREW DID NOT COMPLY WITH COMPANY & FAA PROCEDURES IN COMPUTING THE CG. DRG FLT, UP TO 3/8 INCH OF ICE ACCUMULATED ON THE ACFT'S LEADING EDGES. THERE WAS EVIDENCE THE CREW LOST CONTROL OF THE ACFT AS THE FLAPS WERE LOWERED. THE RGT FLAP ACTUATOR WAS FND IN THE 7 TO 12 DEG POSITION & THE STABILIZER TRIM WAS FND AT THE FULL NOSE DOWN POSITION. FLT TESTS SHOWED THERE WOULD BE NO SIGNIFICANT DIFFICULTY IN CONTROLLING THE ACFT WITH UP TO 1.5' OF ICE ON THE LEADING EDGES & THAT STATIC STABILITY WOULD DETERIORATE DRG FLAP EXTN WITH THE AFT CG CONFIGURATION.