Walkoff is different in different situations and with different materials.  Second harmonic generation (SHG) and third harmonic generation (THG) can be accomplished in LBO and with other materials.  For example, we could use one LBO SHG crystal and one LBO THG crystal.  If we have beams with high peak powers then we can use short crystals.  However to boost the efficiency of the THG process, we often want to make the crystals much longer.  Read on for more about walkoff problems and compensation.