CHARTER FLT SLIDES OFF END OF WET RWY ON LNDG.

Narrative

I HAD PICKED UP THE AIRPLANE AT ADDISON ARPT (ADS). WX WAS HARD IFR; RAIN AND FOG; POOR VISIBILITY THROUGHOUT THE AREA WITH 300 FT CEILINGS AT ADDISON (ADS) AND DALLAS LOVE FIELD (DAL). I NEEDED TO TRANSPORT THE AIRPLANE TO REDBIRD (RBD) AND MAKE 2 LNDGS TO MEET 90 DAY CURRENCY REQUIREMENTS IN CLASS BEFORE FLYING MY PAX MISSION. I FLEW IFR; ADS DIRECT DAL; FLEW AN ILS 13L TO A FULL STOP LNDG; THEN IFR DAL DIRECT RBD; ILS 31 TO A FULL STOP. CEILING AT RBD WAS 400 FT; RPTED BY MYSELF. BRAKING ACTION ON BOTH RWY 13L DAL AND RWY 31 RBD WAS FAIR. SEVERAL MINOR DELAYS AND LAST MIN DETAILS DELAYED MY TKOF. (MISSION WAS AN AIRBORNE WEDDING CEREMONY.) FLT PLAN WAS DELAYED SEVERAL TIMES; CAUSING CHANGES IN THE CLRNC WHICH HAD TO BE EXPLAINED TO THE COUPLE ENRTE. (OBJECTIVE WAS TO SAY WEDDING VOWS 1 MI AGL ABOVE DALLAS.) IFR FLT PLAN WITH RADAR VECTOR NAV WAS SELECTED DUE TO TFC SENSITIVE AREA. ENRTE; RETURNING TO RBD; VFR CONDITIONS ALLOWED VISUAL SIGHTING OF RBD WHILE OVERHEAD DAL HDG S; JUST AFTER CLRNC FOR VOR 17 RBD WAS RECEIVED. UPON RECEIPT OF CLRNC FOR VOR 17 APCH I HAD COMMITTED TO LAND ON RWY 17 OUT OF HABIT FROM PRIOR IFR APCHS WITH LOW CEILINGS. (RWY 13/31 IS LONGER.) IT HAD BEEN A LONG TIME SINCE I HAD FLOWN AN AIRPLANE WITH MPH ON OUTSIDE ARC AND I REFED THE INCORRECT SCALE. I SELECTED 105 MPH (90 KTS) APCH SPD BUT ACTUALLY REFED THE KTS SCALE. AIRSPD WAS ACTUALLY 110 KTS; RATHER THAN THE 110 MPH I BELIEVED I HAD 'OVER THE FENCE'; CAUSING TOUCHDOWN POINT 1/3 OF THE WAY DOWN THE RWY RATHER THAN THE TARGETED 500 FT POINT. I BELIEVED I HAD ENOUGH RWY; ASSUMING I HAD THE SAME BRAKING EFFECTIVENESS AS ON RWY 31/13. I DID NOT. BRAKING ACTION WAS POOR. AS I SLOWED THE AIRPLANE DOWN; I BELIEVED I HAD SLOWED ENOUGH TO TURN OFF ONTO THE TAXIWAY (L TURN) AT THE DEP END. ON THE PAINTED SURFACE (RWY STRIPES AND NUMBERS) I HAD NO TRACTION AND HAD TO GIVE UP THE TURN; SLIDING OFF THE END OF THE RWY AT AN ANGLE AND HITTING 2 BLUE END LIGHTS AT NORMAL TAXI SPD; 1 WITH EACH PROP. (I HAD ALSO FEARED BOGGING DOWN THE NOSE GEAR IN THE SOD AND FLIPPING HAD I GONE STRAIGHT OFF THE THE RWY CENTERLINE.) THIS WOULD HAVE AVOIDED HITTING THE LIGHTS. PROPS STRUCK THE BULBS AND LENS COVERS AT AND NEAR THE TIPS OF 1 BLADE ON EACH ENG. DALLAS FSDO INSPECTOR WAS CONCERNED ABOUT AIRPLANE'S BRAKES CONDITION.