Bumot pannier rack with non-Bumot top case?

I'm leaning towards a Bumot Defender (not Evo) pannier system for my 2009 F800 GS but the top case is either too small (25) or too large (41).

Has anyone mounted a non-Bumot top case such as Touratech/BMW/Givi to the Bumot pannier frame using the relevant adapter?

Here's what the Bumot frame looks like...