JS are mounting their XPDR antennas in the fin. An elegant, low drag solution. If by ADB-B you're referring to out, your XPDR is going to do that job for you, ie. same antenna. If you're referring to the antenna of a certified GPS source such as a Trig TN70 or Freeflight 1201 then I've only seen external mount antennas. Having said that, I don't believe the manufacturers consider gliders at all as they are the standard, surface mount, 'do not paint' variety you find on metal aircraft. Shame really.

CJ