[racket] typed racket and generic interfaces, is there a workaround using properties?

Do generic interfaces work using structure type properties, and if they do, is there a way to use generic interfaces through properties so that I can do it in typed racket?  

Specifically I’m trying to use the gen:custom-write and gen:dict generic interfaces.  I can use prop:custom-write for the first one, but I don’t know what to do for gen:dict.  

Otherwise I’ll just put it in an untyped submodule.