Some time back, Cliff apparently implemented a cab impedance model based on directly-measured (as opposed to component-based modeled) data, but AFAIK he did not provide a means for a user to import impedance data from their measurements. I'm guessing that Dyna-Cabs provides a means for a third party - apparently someone who's willing to jump through the FAS-required hoops (including renting the robot) - to acquire impedance data and associate it with a collection of IRs. There are a number of challenges to making this kind of feature available, primary among them being that, to be useful in a modeler, impedance data will have to be calibrated to an defined absolute reference. Cab response data need not be calibrated in this manner to work in an IR.