PLT OF PVT SMA FAILED TO OPEN INTL FLT PLAN.

Narrative

I WAS FLYING FROM EASTSOUND; WA; MY HOME BASE; TO SYDNEY; BRITISH COLUMBIA AND THE ARPT OF ENTRY FOR VICTORIA. EASTSOUND IS ON AN ISLAND IN THE SAN JUAN GROUP OF ISLANDS; AND THE DISTANCE TO SYDNEY IS ABOUT 15 MI. I HAD FILED A VFR FLT PLAN BY PHONE WITH SEATTLE FLT SVC; BUT FAILED TO ACTIVATE THE FLT PLAN BY RADIO ON TKOF FROM EASTSOUND. I PROCEEDED TO SYDNEY AND LANDED WITHOUT INCIDENT; BUT BECAUSE I HAD NOT ACTIVATED MY FLT PLAN; I WAS IN VIOLATION OF THE APPLICABLE REGS. THE CANADIAN AUTHS SEEMED TO UNDERSTAND AND; AS FAR AS I KNOW; DID NOT PRESS THE ISSUE. I HAD TELEPHONED CANADIAN CUSTOMS PRIOR TO LEAVING FOR THE ARPT SO THEY HAD THEIR REQUIRED NOTICE. OBVIOUSLY I SHOULD HAVE CALLED SEATTLE ON TAKING OFF. HOWEVER THE VISIBILITY AND CEILINGS WERE MARGINAL VFR AND MY IMMEDIATE PREOCCUPATION WAS TO CONTACT VANCOUVER APCH AS SOON AS I WAS AIRBORNE TO GET RADAR COVERAGE INTO SYDNEY. IN MY HASTE TO DO SO; I FORGOT ABOUT ACTIVATING MY FLT PLAN. EASTSOUND IS SO CLOSE TO BOTH THE CANADIAN-UNITED STATES BORDER; AND TO VANCOUVER; THAT THE AIRSPACE OVER EASTSOUND HAS BEEN CEDED BY SEATTLE CTR TO VANCOUVER. SYDNEY IS SO CLOSE THAT I CAN SEE THE RWY LIGHTS FROM MY MOUNTAIN TOP HOME ON A CLR NIGHT. ALL OF THIS MADE ME COMPLACENT AND CARELESS.