Stocking 6 inch HSB with 3-4 inch RES and HBG will not be a problem from a predation stand point. There will need to be food for them all in addition to supp feeding. I would suggest you first put in FH (20 lbs) and some spawning structure for them.
20 lb of FHM in a 1/4 acre pond? gulp - maybe I need to recalculate my plans...