Bobbar,
I have both, the OEM top box and I purchase not too long ago a Givi trekker 46L as my top box, also the Altrider rack.
It fits well, looks good and if I twist the lid of the side case just a tad while opening, it works without removing any cases.
I didn't search for you intended top box yet, but I have a few pictures of my panniers, although I don't think it would help, it can be deceiving.
I am in Jax but traveling right now, we could arrange a Florida meet sometime.