FLC OF CPR LTT ACFT OVERSHOT DSCNT ALT DURING VECTORS TO FINAL APCH.

Narrative

UPON APCH TO HIB THE WX VISIBILITY WAS HAZY. DULUTH APCH; THE CTLING ATC; WAS GIVING US VECTORS FOR THE HIB ILS RWY 31. WE BROKE OUT OF THE CLOUDS BUT STILL THE ARPT WAS TO OUR L APPROX 6 MI. NOT IN SIGHT. IT WAS AT OUR 9 O'CLOCK POS. OUR HDG WAS 120 DEG. I REQUESTED VECTORS FOR THE VISUAL APCH. DULUTH GAVE US A HDG OF 360 DEG. WE WERE DSNDING TO ASSIGNED ALT OF 3500 FT. WE TURNED TO 360 DEGS; TUNED IN THE LOC TO HIB 31 TO INTERCEPT TO AID IN GUIDING TO THE RWY. DURING THE TURN TO 360 DEG WE DSNDED TO 3100 FT WHEN DULUTH REMINDED US TO MAINTAIN 3500 FT. AT THAT POINT WE WERE VFR (ARPT STILL NOT IN SIGHT) AND REQUESTED IFR CANCELLATION WITH DULUTH. OUR CANCELLATION WAS RECEIVED. WE PROCEEDED TO THE ARPT (HIB) AND LANDED. CHAIN OF EVENTS. WE WERE IN THE DSCNT FROM OUR CRUISE ALT; DEVIATING AROUND RAIN SHOWERS VIA OUR RADAR SCREEN DURING THE DSCNT; LOOKING FOR THE ARPT IN THE HAZE; GETTING VECTORS AND TURNING. THE COPLT (THE PF IN THIS CASE) WAS INEXPERIENCED (LESS THAN 500 HRS TOTAL TIME) AND THE PIC (PNF IN THIS CASE) HAD JUST COME OFF A 2 1/2 WK VACATION AND WAS NOT AS SHARP ON PLANNING AHEAD AS HE SHOULD HAVE BEEN COMPARED TO WHERE HE WAS IN PROFICIENCY JUST BEFORE HIS VACATION. BEING TOO BUSY WITH RADIO FREQ CHANGING THE PIC ALLOWED THE ACFT TO DSND BELOW ASSIGNED ALT. AT THE POINT OF BEING REMINDED OF THE ASSIGNED ALT BY ATC; WE JUST CANCELLED IFR; INTERCEPTED THE HIB LOC PROCEEDED INBOUND AND LANDED WITH APPROX 3 MI VISIBILITY IN HAZE.