C172 PLT QUESTIONS THE SAFETY OF CHANGING ALT TO COMPLY WITH VFR ALT HDG RULE WHILE FLYING A NEAR N-S COURSE.

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WHILE FLYING ALMOST DIRECTLY S; I HAD SELECTED A CRUISE ALT OF 6500 FT BASED ON A SLIGHTLY W OF S COURSE OVERALL. HOWEVER; DURING PART OF THE FLT; MY COURSE WENT SLIGHTLY TO THE E OF S (TO AVOID HIGH TERRAIN); WHICH WOULD INDICATE AN ODD ALT +500 FT. BECAUSE MY OVERALL COURSE WAS SO CLOSE TO S; I THOUGHT IT WOULD BE APPROPRIATE TO MAINTAIN A SINGLE ALT RATHER THAN CLB OR DSND. I WAS USING FLT FOLLOWING AT THE TIME; AND THE ATC CTLR ASKED WHAT MY FINAL CRUISE ALT WOULD BE. I SAID 6500 FT; BUT THEN WONDERED IF I SHOULD HAVE CHANGED TO AN ODD ALT FOR THE PORTION OF THE FLT THAT WAS SLIGHTLY EASTERLY. I WAS NOT USING THE AIRWAYS; FLING GPS DIRECT AS MUCH AS POSSIBLE TO SHORTEN THE FLT. LATER IN THE FLT; I DID CLB TO 7500 FT; AFTER CLRING IT WITH ATC; PRIMARILY TO OBTAIN ADDITIONAL TERRAIN CLRNC. NO PROB OCCURRED; I JUST FELT UNEASY WITH WHAT ALT WAS APPROPRIATE. AIRWAYS OR FLTS THAT ARE VERY CLOSE TO 360 TO 180; AND PERHAPS CHANGE SLIGHTLY TO EASTERLY/WESTERLY WOULD INDICATE PER THE REGS A REQUIREMENT TO CHANGE ALTS EACH TIME THAT THE COURSE CROSSES 180/360. IN THE INTEREST OF SAFETY; IT WOULD SEEM TO CREATE AN UNSAFE CONDITION IF YOU HAD OPPOSING TFC BOTH CLBING/DSNDING IN ATTEMPTING TO KEEP WITHIN THE REGS.