The only time I started the engine in feather was if I was on an ice covered ramp. Otherwise, prop fwd before start-up. There is never a need to put the thing in beta in flight. It's a caravan..you can put the 1st notch of flaps in at redline 175kts. I used to hold 160 to a 1 mile final then drag it up. Of course if you do this with pax on board it would scrare the crap outta them so unless it's a freight operation I wouldn't recommend that procedure.
When I used to fly skydivers and freight in the 'van, we never used beta at all in flight. Flight idle and full flaps, the VSI would peg at 6000FPM descent (at about 120kts, as I remember. Haven't flown a Caravan in over 10 years), and we would be back on the ground in less than 4 minutes from 14,500 MSL. Usually beat the last two tandems down.
We also used to start in feather on every start. Company procedure, as per FlightSafety (at the time, this was back in the early '90's, they may have changed that). It was never an issue with the engine or prop, for that matter.
Your AFM should spell it out for you how to do it, rewriting it is a bad idea. from what I understand, we had a placard in the Saab about going below flight idle since some idiot wanted to see what going below it would do and how fast he could slow down and go down. The rumor I heard was that the result was an emergency landing with all the props shattered.