PVT PLT OF AN SMA SEL FAILED TO FLY AT ASSIGNED ALT DUE TO TURB AND LOCATION OF ACFT 'CTR OF GRAVITY.'

Narrative

I WAS UNABLE TO SMOOTHLY CTL ALT IN MY ACFT IN TURB AT THE REARWARD END OF THE CTR OF GRAVITY ENVELOPE. 300 FT FLUCTUATIONS IN MY ALT OCCURRED WHILE I WAS TRANSITIONING FROM MY CLRNC AS FILED TO AN UNFAMILIAR ARR PROC WITH ALMOST NO NOTICE BY ATC; THEN MY CLRNC WAS AMENDED ANOTHER 2 TIMES; PRIOR TO ME RECOVERING FROM THE LAST MIN CHANGES PRIOR TO MY ARR. AFTER LNDG; I RELOADED MY ACFT MORE TO CTR CTR OF GRAVITY AND MY ALT FLUCTUATION IMPROVED CONSIDERABLY. ATC COULD HAVE GIVEN ME MORE NOTICE AND I WOULD HAVE PERFORMED BETTER. I SUPPOSE IT WAS A GOOD EXPERIENCE TO SEE WHAT A DIFFICULT TRANSITION IT CAN BE IN TURB AND WITH RAPID CHANGES AND INSTRUCTIONS FROM ATC. THERE WAS APPARENTLY NO DANGER; BECAUSE THERE WAS NO TFC IN MY VICINITY. I WOULD FEEL BETTER ABOUT MY EXPERIENCE IF THE CTLR HAD BEEN MORE SUPPORTIVE AND TOLERANT GIVEN THE SIT; BUT I FELT A MORE ANTAGONISTIC ATTITUDE FROM THE CTLR PREVAILED; WHICH ADDED TO MY FRUSTRATION AND DIFFICULTY. I FREQUENTLY FLY IN CONGESTED AIRSPACE IN CHICAGO AND I AM USED TO FREQUENT; FAST COM. HAD MY PLANE BEEN BETTER LOADED; THERE BEEN LESS TURB (CONTINUOUS MILD TO MODERATE) AT THE END OF A NEARLY 4 HR SOLO FLT; AND IF ATC HAD NOTIFIED ME ENRTE INSTEAD OF ON ARR; THE ENTIRE SIT WOULD HAVE BEEN GREATLY IMPROVED.