A C172 HAS A GND CONFLICT WITH A LNDG EXTRA 300 GA ACFT THAT ATTEMPTED A LONG LNDG OVER THE C172 ON RWY AT UMP; IN.

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I WAS PREPARING TO DEPART FROM UMP IN OUR CESSNA 172. THE ACTIVE RWY WAS RWY 33. THE ARPT WAS VERY BUSY; SINCE THIS WAS THE BEST WX WE HAD IN SEVERAL WKS AND IT WAS SATURDAY MORNING -- UMP IS NON TWRED. I WAS LISTENING TO CTAF 122.8 DURING TAXI AND RUN-UP OPS TO BECOME FAMILIAR WITH TFC IN THE PATTERN. BEFORE DEPARTING; I HAD TO WAIT AROUND 5 MINS DUE TO 3 OR 4 LNDG ACFT. EVENTUALLY; RWY 33 WAS CLR AND THE NEAREST LNDG ACFT (IN THE PATTERN) WAS ON DOWNWIND FOR RWY 33. I TURNED MY PLANE TO THE E TO SCAN FOR TFC; AND HEARD THE INCOMING TFC ANNOUNCE STARTING L BASE FOR RWY 33. WE COULD NOT SEE THE AIRPLANE YET; AND ANNOUNCED DEPARTING RWY 33. I TAXIED ONTO THE RWY AND BEFORE WE COULD EVEN COMPLETE OUR TURN FOR RWY ALIGNMENT; THE INCOMING PLANE ANNOUNCED 'CESSNA; HOLD SHORT OF RWY 33 FOR LNDG TFC ON SHORT FINAL!' THIS WAS 5-10 SECONDS AFTER HE HAD ANNOUNCED STARTING L BASE. I WAS TURNING MY PLANE AROUND TO RETURN TO THE TXWY WHEN A SHADOW PASSED RIGHT BY US AND THEN I SAW AN EXTRA 300 TOUCH DOWN ON THE RWY. FOR WHATEVER REASON; HE TOOK OFF AND MADE A GAR; PROBABLY BECAUSE HE WAS GOING TOO FAST AND HAD LANDED SLIGHTLY LONG. THE EXTRA 300 MADE A VERY CLOSE; FAST PATTERN AND CAME BACK AND LANDED AROUND 30 SECONDS LATER. I BELIEVE THE FOLLOWING ITEMS CONTRIBUTED TO THIS NEAR MISS: 1) THE EXTRA 300 WAS FLYING A NONSTANDARD; CLOSE-IN AND FAST TFC PATTERN; WHICH DID NOT CONFORM WITH OTHER EXISTING TFC. 2) THE ARPT WAS VERY BUSY AT THE TIME. 3) THE EXTRA 300 TRIED TO LAND EVEN THOUGH I HAD TAXIED ONTO THE RWY; INSTEAD OF IMMEDIATELY GOING AROUND. 4) THE EXTRA 300 PLT WAS VERY AGGRESSIVE AND INCONSIDERATE OF ALL OTHER ACFT IN THE VICINITY. CONTRIBUTING FACTOR: I HAD ASSUMED OTHER ACFT WOULD BE FLYING A STANDARD TFC PATTERN (DIMENSIONALLY) AS DEFINED IN FAR/AIM AND OTHER REF TEXTS.