DEPARTING PAO WITH A PLAN TO AVOID SFO CLASS B A C182 PLT CLBS TOWARD THE CLASS B FLOOR TO AVOID TFC BEING VECTORED IN HIS DIRECTION BY APCH CTL. THE QUESTION WAS RAISED BY THE TRACON AS TO WHETHER OR NOT THE CLASS B HAD BEEN ENTERED WITHOUT CLRNC.

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AFTER DEP FROM PAO VIA A R DUMBARTON DEP; I PLANNED TO CLB TO 3500 FT UNTIL BEYOND THE SFO DME 20 CIRCLE THEN CLB FURTHER IN STEPS TO AVOID CLASS B AIRSPACE. MY RTE OF FLT WAS PAO DIRECT IMPLY DIRECT TCY (ARPT) DIRECT FAT. AT APPROX ABEAM KGO ANTENNAS; PAO TWR APPROVED A FREQ CHANGE. I THEN SWITCHED TO LISTEN TO BAY APCH SECTOR. I THEN HEARD A SMALL PLANE SOMEWHERE NEAR SUNOL SETTING UP FOR A PRACTICE VOR APCH TO HWD. BAY APCH HAD HIM STAY NEAR 3500 FT AND VECTORED TOWARDS ME. IN ORDER TO AVOID THE ACFT I CLBED TO 3900 FT; JUST BELOW SFO CLASS B. MY ALTIMETER HAD BEEN SET AT PAO TO 29.88. I REALIZE IT IS NOT WISE TO GET SO CLOSE TO CLASS B FLOOR WITHOUT CLRNC; BUT FELT THAT IT WAS THE SAFEST PLACE TO BE GIVEN THE TFC. BAY APCH CALLED LATER TO SAY THAT I MAY HAVE VIOLATED CLASS B AIRSPACE. MY INSTS SAY I DID NOT. HOWEVER; I STILL BELIEVE IT WAS AN UNSAFE SIT. BAY APCH TOLD ME THAT THEIR MVA IN THAT AREA IS 4000 FT EVEN BEYOND 20 DME WHERE THE CLASS B FLOOR IS 6000 FT. THE WHOLE SECTOR IS AN ACCIDENT WAITING TO HAPPEN.