New member, so probably not best info. However, my pond is half your size and the stocking plan recommended to me by a pond management company was 10 6-8" LMB. I have a known Green Sunfish over-population and like you want a decent BG fishery.
A 6-8" LMB can consume any panfish under 3" and will grow to about 12" in a year or two. You may lose some Tilapia though.
