Small-angle X-ray and neutron scattering are used in conjunction to study structures in a poly(dimethylsiloxane) network having a bimodal distribution of network chain lengths, a type of elastomer of considerable interest because of its unusually good mechanical properties. The scaling regimes for the scattering are compared and contrasted for varying degrees of network swelling. The excess scattering at small angles in the swollen state is associated with large-scale structures, likely high cross-link density clusters with reduced swelling, topologically trapped within the network mesh. These results indicate the presence of supramolecular structures with apparently smooth surfaces even in the non-swollen state for this type of elastomer. Optical microscopy of unimodal and bimodal elastomers having comparable crosslink staining does in fact suggest the presence of smooth surfaced, micron-scale islands of higher cross-link density. Finally, the effects of the molecular weight distribution of the network mesh demonstrate that bimodal networks can have supramolecular structures that are smaller but more random than their unimodal counterparts.