Flaps don't really help much unless you are maxed out in the vert you can use full rudder to pop the plane over while popping the flaps. In a straight up luftberry on the deck you will in fact do better using no flaps.
Thats being said they are not useless, I do use them a lot but only when I have my opponent in a bad situation to start with. Flying a Dora well is about getting your opponent in that situation, if it looks like I am matching a guys spit in a turn I am just not in the way he is turning, that would be impossible.
Usually I match an opponent's turn radius by using slow roll in the vertical to match his turn in the horizontal, see my rubbish illustration by the time he tries to yank his plane vertical for the shot he has burnt all his E turning and cannot get guns, you can see roughly that the red plane is using mostly turn elevator throughout the move and I a elevator for a short but sharp period at the start to get my nose vertical then used the Dora's precise roll qualities match his turn, note I do not want to be in guns at this stage I am staying out of guns and tempting the spit to keep on turning and stay slightly above him timed correctly I then fall on him, once I have a plane trapped in this situation at an alt disadvantage and constantly turning through threat of my guns he is never able to gain enough time to regain the energy to maneuver, the Dora has a very powerful engine that few can match in the vertical. The reason most Dora pilots have a problem shooting down cons in a straight up fight is because they let their opponent get back his energy by leaving 5 minutes between each pass
Seen from the top I can sit inside a better turning planes radius conserve more energy and stall out above him.