I have not tried these, though I am curious about them. You would need two of them, and I suspect two would be not much smaller than an MMA6000 preamp.
By the way, I've had some issues with the line-in jack of the MiniR82 coming loose, Trew Audio just repaired one for me (without the trip back to Switzerland). I discovered that using Binder connectors wired for no power, you get the same levels as line in (0 dBu = 0dB setting) with the Binder three-way switch at "0" and the volume knobs at about 11 o'clock. I did three recordings this weekend with that setup in different venues, and was able to use my normal preamp settings (on the MMA6000).
Jeff