A mounting collar comprises a collar body comprising an opening for receiving at least a portion of an electronics component (e.g., capacitor) of an electronics assembly, and a radial retention component supported about an inner surface (e.g., annular groove) of the opening of the collar body. The radial retention component (e.g., elastomeric O-ring) is operable to apply a radial force on the electronics component to at least partially support the electronics component. A mounting system comprises a first mounting collar for mounting a first electronics component to a support structure, and a second mounting collar for mounting a second electronics component to the support structure. The first and second mounting collars can be nested together to minimize a distance between the first and second electronics components. The first and second mounting collars can each comprise an elastomeric O-ring to reduce strain between the electronics components and the circuit board. Associated systems and methods are provided.