I installed a blade antenna in the recommended location for my Discus
2 just behind and to one side of the gear door and an internal ground
plane about 6" square. It works very well in this location (also had
a short coax from the transponder, which is a consideration at these
higher frequencies).

Tim is absolutely right, though. It is physically a right royal pain
in the ass. I don't know anyone who has one in this location who
hasn't broken it as it is perfectly located to snag on the trailer
ramp. I have a short quarter wave monopole as back-up. This will be
my default the next time the blade breaks! I doubt that the extra
drag is worth worrying about.

If you can locate the blade above and behind the cockpit, this is a
much safer location and I have seen a couple of these installations
that also work well.

Mike