Separating generated flatbuffer/protobuf files from domain model - best practices

Question

I'm using flatbuffers for the first time. I've generated my java classes and have tested out serializing / deserializaing a message. Now I'm thinking about how to integrate these in to my JavaFx and Android applications.

Is it valid to pass a DataMessage or a MessageA directly in to bussiness logic classes or my UI? It's seems really unwieldly to pass the DataMessage and then have to extract the correct payload type. So, I created wrappers around each type, so I have MessageAWrapper that contains the MessageA and Header. Should the client/UI code directly access the values from a MessageA, or is it a better practice to copy all the fields from MessageA in to new primitives defined in MessageAWrapper. Doing so seems against what Flatbuffers is for, but I also feel dirty exposign the MessageA that has flatbuffers-specific parsing methods and such. But, it's also a bit of work to have my wrapper classes copy over fields and store them, and could be error prone. But, at somewhere in my stack, I may want to, say, stuff a latitude/longitude float pair in to a convenience class called GeographicPosition. I can do this easily in a wrapper.

So I'm asking for what's the best practices for using flatbuffers / protobufs in an application wrt abstraction / separation of concerns. Most examples I see are just doing quick serialization to compare speed to JSON parsing, and I'm not seeing a full-up practical example of using it in an application to, say, stuff values in to UI controls.

For reference, I created a flatbuffers schema as follows:

table MessageA{
    myVal1:float;
    myVal2:float;
    myVal3:int;
}


union MessagePayload { MessageA, MessageB, MessageC }


// top level message class. Contains a header, and a payload consisting of one of the message types specified in the MessagePayload union.
table DataMessage {
    header:Header (required);
    payload:MessagePayload (required);
}

root_type DataMessage;

I do this so I can examine the payload type to determine what payload I have and serialize that.