HDG TRACK DEV IN A NON ADHERENCE TO ATC CLRNC.

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ENRTE FROM SAC TO HMT ON IFR FLT PLAN AND CLRNC. VFR ON TOP AT 7500 FT; WX CEILING AND VISIBILITY UNLIMITED. ROUTING ON CLRNC CALLED FOR V23 FROM LINDEN VOR TO SHAFTER VOR. DURING MY IFR TRAINING; I WAS TOLD THAT DECLARING 'VFR ON TOP' ALLOWED DIRECT ROUTING AT PLT'S DISCRETION. I CAN RECALL SPECIFIC EXAMPLES MY CFII GAVE. AS A RESULT; I OPTED TO DEPART LINDEN DIRECT EL NIDO DIRECT SHAFTER. I DIDN'T REQUEST AN AMENDED CLRNC OR ADVISE ATC; NOT BELIEVING IT TO BE NEEDED/REQUIRED. CASTLE APCH QUESTIONED MY ROUTING AFTER I WAS OFF MY ASSIGNED RTE AND I ADVISED THEM OF MY INTENTIONS. APCH ADVISED THAT I WAS REQUIRED TO FLY THE ROUTING IN MY CLRNC. CASTLE THEN AMENDED MY CLRNC TO ALLOW ME TO PROCEED DIRECT SHAFTER. I WOULD NEVER KNOWINGLY VIOLATE THE FARS; BUT NEITHER HAVE I READ THEM AND THE AIM COVER TO COVER AND WORD FOR WORD. I HAVE RELIED; AT LEAST IN PART; ON THE INFO IMPARTED TO ME BY INSTRUCTORS. I GUESS I WILL HAVE TO BE MORE SKEPTICAL AND DO MORE PERSONAL RESEARCH INTO THESE ISSUES IN THE FUTURE.