Narrative:

While flying almost directly south, I had selected a cruise altitude of 6500 ft based on a slightly west of south course overall. However, during part of the flight, my course went slightly to the east of south (to avoid high terrain), which would indicate an odd altitude +500 ft. Because my overall course was so close to south, I thought it would be appropriate to maintain a single altitude rather than climb or descend. I was using flight following at the time, and the ATC controller asked what my final cruise altitude would be. I said 6500 ft, but then wondered if I should have changed to an odd altitude for the portion of the flight that was slightly easterly. I was not using the airways, fling GPS direct as much as possible to shorten the flight. Later in the flight, I did climb to 7500 ft, after clearing it with ATC, primarily to obtain additional terrain clearance. No problem occurred, I just felt uneasy with what altitude was appropriate. Airways or flts that are very close to 360 to 180, and perhaps change slightly to easterly/westerly would indicate per the regulations a requirement to change altitudes 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 traffic both climbing/descending in attempting to keep within the regulations.

Related reports:

Google
 

Original NASA ASRS Text

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

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.