I don't think 40/1 is remotely unreasonable for the Perkoz, even with
that "big clunky fixed gear hanging down." It has 20m in wing span and
a decent aspect ratio. Compared to the Duo Discus and the DG500/1000
series, it's about 4-5 pts less in best L/D or about a 10% hit in
performance. Seems very reasonable to this professional aerodynamicist.