no, your peak will be probably a little higher than that, it might be mid-high 30s. if youve got acess to a termlab, run a sweep and find your loudest frequency.
No. 33~50 if your gonna run a sweep. Unless you want to see the major difference below and above tuning. Then run the sweep from 20Hz. Reason I say no is because from 20-28 would just be a waste of time, producing very low number.