I have a Becker ATC 4401 Mode C transponder in my EX. I like it for the most part, (when it is cold outside it will sometimes will develop a fault) The size, weight and minimal panel space are the big draw for me. I'm thinking now though about a ADS-B type transponder and am wondering if others have experience with a similar size unit that meets the new requirements?

I am installing a Garmin GTX 335 in another plane but it is a standard stack size unit and I'm interested in the 2.25" instrument hole size. But so far I'm not finding much.

I have a Garmin 796 and a GDL 39 3D for the In side of the system and move that between the two planes. Maybe the GPS in the GDL will work for the WAAS requirement in an Experimental?

Thanks for any help and suggestions.