The airfoils on the Standard Libelle (201) and the H301 Libelle are different. The 201 uses the (Wortmann) FX 66-17AII-182 airfoil, which is 18.2-percent-chord thick. Wil Schuemann brilliantly observed that the 301 airfoil is very similar to an FX 67-K-XXX airfoil except near the leading edge---thus the leading-edge "extension" of the Schuemann modification.

Dan Somers
Port Matilda, Pennsylvania, USA