This brings up another question and complication regarding the
installation of transponders in sailplanes. The altimeter. I get a
different answer everytime I ask it, but the transponder inspection
may/may not include inspection of the altimeter. I had to install an
IFR altimeter (large size) to pass the original installation
inspection. I could not find a small size altimeter that met the
accuracy requirements. Subsequent inspectors didn't care so I went
back to my small altimeter.

Guy Acheson "DDS"