Anyone that has followed my builds or seen my instruments will know that I'm a huge fan of "floating blade" style bridges combined with a "Zero-Fret" string guide/nut. I have found this combo to be one of the most consistent ways to achieve low string action. I'm going to now share with you one of my secrets to how I make my floating bridge the correct height.
I use a simple wedge feeler gauge. I locate where the bridge will sit on the soundboard, and slide the feeler gauge under the string. I then check the action and adjust the gauge until I have the action that I want. I mark that height on the gauge with a pencil. I then take the gauge to my bridge material and mark that height. I then draw out my bridge design, cut and finish.
I hope this little tip will help you.