Well, I guess it depends on where your bullets are impacting at this time with your chosen load.
If you are happy with your load and your POI and Dawson has told you they do not sell a sight of the correct height to maintain the current condition, then you are out of luck (at least for a Dawson F/O sight).
If you don't mind a POI change, then it appears Dawson provided you with some sound advice, and you can follow their web page math formula to calculate what you need. Unless your gun has an unusually tall or unusually short front sight, you should be able to obtain a F/O front sight that puts your POI very, very close to your desired location at 20 yards or so.