This study engineered multivalent nanobody-based proteins, termed "Quads," that fuse anti-α-cobratoxin nanobodies to a p53 tetramerization scaffold to increase valence (up to 16 binding sites), size and endosomal recyclability, improving neutralization of long α-neurotoxins from elapid snakes such as cobras. Flow Induced Dispersion Analysis (FIDA), on a Fida 1 instrument, was used to measure the binding affinity and hydrodynamic size of the nanobody and Quad constructs bound to α-cobratoxin, confirming affinity was retained and all nanobody domains stayed accessible in the multivalent scaffold. It is an example of using FIDA to confirm binding affinity and size of engineered multivalent proteins in solution.