RV6A PLT TAXIES ONTO THE RWY AT A NON TWRED ARPT CAUSING AN ACFT ON SHORT FINAL TO GO AROUND.

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I HAD FINISHED MY RUN-UP; AND HEARD A CESSNA ANNOUNCE; BUT WAS NOT ABLE TO HEAR THE POS. I LOOKED UP AT THE APCH END OF RWY 21; AND SAW A CESSNA TURNING BASE. I ANNOUNCED I WAS TAKING THE RWY; AND STARTED TO ROLL. I HEARD SOMEONE CALL THEY WERE ON FINAL; AND LOOKED AGAIN AND SAW ANOTHER CESSNA ABOUT 80 YARDS FROM THE THRESHOLD ON FINAL. I STEPPED ON THE R BRAKE AND WHEELED BACK TO THE TXWY; BUT THEY WERE FORCED TO GO AROUND. I REALIZED THAT THEY HAD BEEN IN THE BLIND SPOT CAUSED BY MY ROLL BAR AND CANOPY RIM. AS THEY WERE COMING RIGHT AT ME; THEIR POS IN THE CANOPY DID NOT CHANGE. MY FIRST MISTAKE WAS ASSUMING THERE WAS JUST 1 CESSNA IN THE PATTERN. MY SECOND MISTAKE WAS NOT ASKING FOR A REPEAT OF THE UNCLR CALL. THE THIRD WAS NOT MOVING MY HEAD DURING THE AREA SCAN; TO BE SURE NOTHING WAS HIDING BEHIND THE BLIND SPOT. NOW I KNOW 1) NOT TO MOVE IN A BUSY PATTERN UNLESS I KNOW WHERE EVERYBODY IS; 2) TO HEAR EVERY CALL CLRLY; AND MOVE MY HEAD DURING THE AREA SCAN TO ELIMINATE BLIND SPOTS. I DON'T BELIEVE THERE WERE ANY PHYSIOLOGICAL CONTRIBUTORS TO MY ERRORS -- JUST BAD JUDGEMENT.