INFLT ENCOUNTER WITH WX; PLT CANCELS IFR TO ALLEVIATE THE PAX BEHAVIOR PHYSICAL DISCOMFORT.

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I'M ON AN IFR FLT PLAN FROM HUF TO JST; ENRTE TO GBR (FINAL). ATC ASSIGNS LOWER ALT. I DSND TO 4600 FT ASSIGNED; WHICH IS NEAR VERY BOTTOM OF CUMULUS LAYER. MODERATE TURB CAUSED DIFFICULTY IN HOLDING ALT -- REMAIN WITHIN 200 FT ON ALT ON VECTORS NEAR JST; APPROX 15 MI OUT. VECTOR TO INTERCEPT; PICKED UP OVER OM. ATC ASKED IF I'D LIKE 'BACK TO GATE.' OK. SO I GET VECTORS WAY OUT AGAIN; IN THE CONTINUED TURB. PAX ARE GETTING VERY SICK. WE ARE FLYING IN AND OUT OF CLOUDS; VFR TO IFR AREAS WHERE THE WHOLE SKY OPENS UP BELOW AND AROUND AND ABOVE. IN ONE OF THESE LARGE OPENINGS; I CANCEL IFR TO AVOID MORE TURB; ATC ACCEPTED CANCELLATION BUT WOULD NOT RESPOND AGAIN WHEN I ASKED TO GO TO TWR. I CALLED TWR AND RECEIVED SVFR TO LAND AT JST. WAS ABOUT 15 MI OUT DSNDING OUT OF 4600 FT. I REMAINED VFR; HAD NO PROB FINDING ARPT; AND LANDED. AN INDIVIDUAL FROM THE FBO YELLED OUT THE WINDOW TO TELL ME TO GO TALK TO THE TWR (QUITE RUDELY). I WALKED OVER AND THE TWR PERSON CALLED ZOB. I SPOKE WITH A SUPVR WHO WAS UPSET ABOUT SOMETHING; WAS VAGUE AND WOULD NOT ELABORATE OR SAY MUCH OF NOTE EXCEPT THAT HE WAS DEFINITELY STARTING 'PAPER WORK.' I GREW QUITE CONCERNED; AND AM SURE THAT I DID NOT VIOLATE ANY RULES; OR ACT IN AN UNSAFE OR CARELESS FASHION. THE TWR CTLR SAID HE HAD 'NO PROB' AND THAT EVERYTHING WAS 'OK' WITH HIM ON THE APCH AND LNDG. HE WAS HELPFUL. THE VECTORS WERE VERY STRANGE; EITHER TOO SHORT AND QUICK OR TOO LONG AND INADVERTENT. TIME OF CONFUSION AFTER CANCELING IFR WAS CREATED BY CTR NOT ANSWERING OR SAYING 'GO TO TWR' OR 'FREQ CHANGE APPROVED' ETC. I THEN FILED IFR AND FLEW TO GBR. TOOK OFF 24 HRS BEFORE TORNADO HIT.