After I installed the transponder antenna I noticed that the mounting plate would not be exactly flush with the fabric. It also states in the Dynon installation guide that the transponder and ADSB antennas must be atleast 24" apart. The two mounting plates in the bottom of the fuselage are to close together to get 24" of separation. I decided to install two new antenna mounts just to the outside of the existing mounts. I made them both out of aluminum and Hysoled the front and outside edge to the fuselage where they will be flush with the buttom of the tubes. Then I ran a level from the bottom outside longeron to the stringer that is run from front to the back of the fuselage down the middle underneath. This shold get me a pretty close estimate as to where the fabric will run underneath. I shimmed the plates to match the level and this should allow them to be flush with the fabric. After the glue dries I will permanently shim and install the inside and rear portion of the plates.