ALTDEV ALT EXCURSION FROM ASSIGNED. INFLT ENCOUNTER WITH TURB.

Narrative

WHILE FLYING AN SMT FOR THE ACFT OWNER TO N ADAMS; MA (2B6) FOR MAINT; THIS PLT STARTED A VFR DSCNT FROM 11500 FT APPROX 10-12 MI NE OF THE PWL VOR. WHILE DSNDING THROUGH APPROX 5500 FT; IT BECAME APPARENT THAT CONTINUED VFR DUE TO SNOW AND DECREASED FORWARD VISIBILITY WAS UNLIKELY. AT THIS TIME A LCL IFR CLRNC FOR AN INST APCH TO THE PSF ARPT WAS REQUESTED FROM ALBANY APCH CTL WITH WHOM THE FLT HAD BEEN WORKING FOR VFR FLT FOLLOWING. A CLRNC WAS ISSUED TO PROCEED DIRECTLY TO THE DXT BEACON TO MAINTAIN 4000 FT AND THE FLT WAS CLRED FOR THE LOC RWY 26 AT PSF. AT THE TIME A SIGMET FOR OCCASIONAL SEVERE TURB WAS IN EFFECT. DSNDING THROUGH 4500 FT; THE ACFT ENCOUNTERED CONSTANT MODERATE TO OCCASIONAL SEVERE TURB. TO PREVENT OVERSTRESSING THE AIRFRAME; PWR WAS REDUCED AT TIMES TO FLT IDLE. EVEN WITH GREATLY REDUCED PWR; THE ACFT WAS UNABLE TO MAINTAIN 4000 FT AND STAY WITHIN 10-15 KTS OF VA. AS A RESULT; THE ACFT SLOWLY CLBED TO 4800 FT AT WHICH POINT THE ALBANY APCH CTLR ASKED THE ACFT'S ALT. I REPLIED '4800 FT; WE'RE JUST TRYING TO STAY OUT OF THE BUMPS' OR SOMETHING TO THAT EFFECT. NO OTHER MENTION WAS MADE BY ALBANY APCH AND I WAS ABLE TO CANCEL IFR INBOUND ON THE LOC PASSING 3200 FT AND CONTINUE VFR TO 2B6. MY CONCERN IS THAT I WAS UNABLE TO MAINTAIN AN ASSIGNED ALT AND WAS SO BUSY TRYING TO STAY IN CTL OF THE ACFT THAT I DID NOT ADVISE ALBANY APCH BEFORE I HAD TO BE ASKED BY THE CTLR. ALSO; IF ANY ACTION IS TO BE TAKEN BY THE FAA; I WANT TO MAKE IT CLR THAT IT WAS I AND NOT THE REGISTERED OWNER/PLT FLYING ON THIS OCCASION.