re: Rack return not required...
I've talked to the end users of the racks.
It would be a rare requirement, but still exists as afar as end user scientists and engineers are concerned.
I'm done here Doug you don't understand how NASA does things if you think because they don't require something it isn't needed.
And other example: they want a single spacesuit from launch to return from the Moon again. Just as they did with Apollo. It's an absurd requirement on the face of it! Nobody will tolerate Scye bearings on launch and return, but they are required on the Moon (if you plan to do any real work).