Personally I would be treating every interaction with DFR as a job interview. Wear what you would wear if you were being interviewed for the position (as realistically that is what is happening). When I went through the process last time I went in full suit and tie every step of the way and I fully intend on doing the same this time around.
If your clothes fit correctly they should be comfortable! How you present yourself speaks volumes, a picture is worth a thousand words after all!