A B727 CAPT LANDED IN THE RWY OVERRUN AFTER DSNDING LOW ON GLIDEPATH.

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PF LINED UP ON FINAL 7+ MI OUT. WAS CONFIGURED FOR LNDG 4+ MI OUT; APCH WAS STABILIZED BY 1000 FT AGL ON DSCNT. ABOUT 1 1/2 MI FROM RWY; PF BEGAN TO DEVIATE BELOW ILS GS. I MADE STANDARD CALLOUTS; IE; '1 DOT LOW;' '2 DOTS LOW;' 'FULL SCALE LOW.' AFTER A MINIMAL FLARE; ACFT TOUCHED DOWN APPROX 1000 FT SHORT OF THE DISPLACED THRESHOLD FOR RWY 9. TOUCHDOWN WAS FIRM; BUT WITHIN NORMAL PARAMETERS. AS PNF; I MIGHT HAVE MADE AN ATTEMPT TO TAKE CTL OF THE ACFT WHEN I SAW THE APCH PATH DEVIATE FROM NORMAL. UNFORTUNATELY; THIS WAS 'NORMAL' FOR THIS PLT AND OTHERS IN THE COMPANY; IE; AN ACCEPTED PRACTICE. DEVIATING BELOW GLIDEPATH ON SHORT FINAL IS BELIEVED BY SOME HERE TO SHORTEN THE LNDG DISTANCE. I DISAGREE AND HAVE FOR SOME TIME LOBBIED TO CHANGE THE PRACTICE; CITING FAR 91.129 AS WELL AS OTHER GUIDANCE. POSTFLT; WHEN I ASKED THE PF IF HE INTENDED TO RPT THE EVENT; HE DENIED IT HAD HAPPENED. THE FOLLOWING DAY HE DID ADMIT TO LNDG SHORT AND SAID HE INTENDED TO RPT IT. AS THE PF WAS ALSO DESIGNATED AS PIC FOR THE FLT. I WANTED TO GIVE HIM THE OPPORTUNITY TO COME FORWARD AND RPT THE EVENT TO THE ARPT MGMNT BEFORE I DID.