GA PLT PENETRATES TFR.

Narrative

DEPARTED ZZZ FOR ZZZ1. RTE OF FLT USING GPS WAS ZZZ DIRECT ZZZ2 DIRECT ZZZ3 DIRECT ZZZ1. IT WAS MY UNDERSTANDING THAT A STRAIGHT LINE BTWN ZZZ2 AND ZZZ3 BELOW 2500 FT WILL KEEP AN ACFT CLR OF THE ZZZ TFR AND THE CLASS B AIRSPACE. I HAVE USED THIS RTE SEVERAL TIMES THIS YR ON TRIPS TO THE EASTERN SHORE OF MARYLAND WITH NO PROBS ENCOUNTERED. UPON LNDG AT ZZZ1; I WAS INSTRUCTED TO CALL A GOV REPRESENTATIVE. I ALSO RECEIVED A CALL FROM ZZZ TRACON. I WAS SURPRISED TO LEARN THAT A COURSE BTWN ZZZ2 AND ZZZ3 WOULD CLIP THE EDGE OF THE TFR. I WAS TOLD THAT I HAD PENETRATED THE TFR BY AS MUCH AS 4 MI. I WAS NOT USING RADAR SVCS BUT WAS MONITORING ZZZ2 APCH ON ONE RADIO AND THE UNICOM FREQS OF ZZZ2 AND ZZZ3 ON THE SECOND RADIO. I HONESTLY FELT THAT I WAS CLR OF THE ZZZ TFR; BUT HAVE BEEN INFORMED BY 3 DIFFERENT AGENCIES THAT I WAS NOT. AS A RESULT; I WILL NOT PASS BTWN THESE 2 AREAS WITHOUT FIRST ESTABLISHING 2-WAY COM; RECEIVING A DISCRETE XPONDER CODE; AND SPECIFIC VECTORS FROM ATC BEFORE FLYING E OF ZZZ2.