Methods and devices for more efficiently engineering diversity into recombinant polypeptides and/or nucleic acids are provided herein. For example, a variety of methods of selecting and/or assessing potential crossover sites in an amino acid sequence or a nucleotide sequence are provided, as well as the resulting chimeric product sequences. These methods include, e.g., consideration of structural, functional and/or statistical data in the selection and assessment of sequences and crossover sites for use in recombination.