I would feed smaller pieces. The feeding argument boils down to what each person would consider 'optimal' health. I consider that to be several things
1) hardiness
2) size (my sebae is around 24")
3) regular sexual reproductive activity separate from stress response.
The latter, in the circumstance of females, may not be good for the tank, but, IME, is a good indicator of the overall health of the animal. I am currently working on spawning behavior in a second H. crispa. IMHO, if you are not going to allow for the potential growth and natural behaviors of a large, healthy anemone, then you should set up a separate tank for it. I assume that most people that have anemones in their tanks primarily focus on that particular animal.