the previous owner of my circa 1900's home put a narrow cove crown moulding up after he redrywalled the ceiling. that moulding is removed and i am about to put up wide crown moulding. is a top and bottom backer board advisable to eliminate the issues around stud finding? or is it not worth the hassle? if so are the top / bottom backer boards extended beyond the moulding edges? if they extend should i run the exposed backer boards through my router to give it a profile? any comments would be helpful - although i'm a handy fellow i've never attempted costly crown moulding installs.
ty