Combining static and dynamic typing within the same language, i.e. gradual typing, offers clear benefits to programmers. However, many open questions remain regarding the semantics of gradually typed languages, pecially concerning the integration of gradual typing with existing languages. I will discuss Reticulated Python, our lightweight system for experimenting with gradual-typed dialects of Python. Using Reticulated Python, we evaluated a gradual type system that features structurally-typed objects and type inference for local variables. I will discuss two dynamic semantics for casts which we implemented and evaluated in Reticulated Python: one based on proxies and one design that instead uses statically-inserted, use-site checks.