The TRF501X is currently undergoing final testing in Japan. At the JMRCA Expert TC champs at Yatabe last weekend Tamiya had both Marc Rheinard and Hupo Honigl present.
Marc was racing at the JMRCA race but apparently Hupo had come along just to test the 501X together with the TRF designers and Marc.
Here's a bad quality picture taken in the pits at Yatabe.
http://kentech.blogs.se/