My primary airplane is a 1929 Waco ATO. The reason I am looking at the Trig solution is that there is no room for much. The panel depth is about 5" and there is no more room. I have a com radio and a transponder and they are in their own enclosure next to my right knee. An antenna on the bottom would work. A larger transponder, more avionics, not so much. I have to believe the Pitts crowd has a similar problem.