Erik, BR-2A will serve you at anytime!
I just wish they had released these double F-mount lenses, I have always disliked the 52mm interface as it has no way of locking, indexing rotation nor fixed length,,,
Sure these mount reversing rings as well as the K-Ring set has the potential for great usage as more or less universal building blocks, I just see the practical and secure part of the use as equal important