You are looking for impact absorption by the structure failing in a way as to reduce the transmitted impact forces to the egg, correct? A biplane will not necessarily be more beneficial. A better bet would be to build a low wing thick airfoil with a lattice type structure to give more material a chance to break during the impact. The fuselage sand landing gear should also have a more complex structure. As the structure fails it will absorb the impact over more time allowing the forces to taper off gradually. Using weaker materials with a more complex structure would be more beneficial. Just my .02.