NMAC AND CRITICAL GND CONFLICT OCCURS AT A NON TWR ARPT UNICOM.

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RPTED TO MARCO ISLAND TFC INBOUND 10 MI OUT FOR LNDG. RPTED 1 MI L BASE RWY 17 ALT 1000 FT. RPTED TURNING FINAL RWY 17 AT 700 FT. LNDG UNEVENTFUL UNTIL 180 DEG U-TURN (NO TXWYS AVAILABLE). RPTED BACK TAXIING ON ACTIVE RWY. LOOKED UP AND SAW A TWIN ENG SEMINOLE ON FINAL APCH 1/4 MI OUT. THEN CALLED HIM ON RADIO TO REMIND HIM THAT I WAS TAXIING BACK. AT THAT POINT NO RESPONSE FROM ACFT; GEAR DID NOT GO UP; AND I REALIZED THAT HE INSISTED ON LNDG. I WAS FORCED TO TAKE EVASIVE ACTION BY TRYING TO GET OFF THE RWY. THE ACFT LANDED AND MISSED MY WINGTIP BY APPROX 10 FT AND THEN PROCEEDED TO TKOF. REMAINING IN THE PATTERN AND CONTINUED TO MAKE TOUCH AND GO LNDGS. I ASKED HIM IF HIS RADIO WAS ON AND HE REPLIED: 'CERTAINLY; BUT I NEVER HEARD ANYTHING FROM YOU.' CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR SAYS ACFT WAS IN A NOSE HIGH ATTITUDE AND PERHAPS THAT IS WHY THE INSTRUCTOR PLT DIDN'T SEE HIM. RPTR COUNSELED ON FAA HOTLINE NUMBER FOR RPTING DANGEROUS INCIDENTS LIKE THIS.