That is pretty low for a full keel and points to a tender boat. If you search and look at several full keelers you would see that the average is over 30%. They need more ballast because for the same dimension full keels had normally less draft.
what is the draft of your boat?
My draft is 5' original ballast was 3200lb then 800 more was added totaling 4000, disp is about 15,000 (27%) still a little tender. Original design called for 13,200 w/3200 ballast (24%), but construction method ended up with a much heavier boat (still riding on design water line). It doesn't take much to get the boat over to 30degree heel, but once there it doesn't want to go any further (builder named the boat "Roll N' Go"), I know, I've tried, it's better to discover your boats limits before they get shown to you.