The following information is not useful to an `IReactorCallback` implementation, and can be passed as `fillData` if actually necessary: * ResolvedOrder.OrderInfo (all fields) * ResolvedOrder.sig * ResolvedOrder.hash * ResolvedOrder.InputToken.maxAmount Reducing the data passed to the function will reduce the memory footprint of the execution scope and therefore the gas. [edit: added to list of unnecessary fields]