Join Date: Apr 2005
Location: Los Angeles, CA, USA
I have the RCU installed. I chose it because 1) it was cheap, 2) the K1200LT version on my LT worked just fine, and 2) at the time I bought it for the GT I didn't know of alternatives.
The problem with the RCU shelf is that it vibrates like nothing else, which can cause things to come loose, and displays (of a GPS) may become unreadable do to the level of vibration.
I only saw the BigMac on photos here, but I think the main difference between the two is that the BigMac also has support in the front (to presumable prevent vibration). The RCU only comes with two 'rear legs' to mount the shelf on.
If you're the tinkering type, you might opt for the RCU and fabricate two front supporting legs, and save some $$$, or buy the BigMac.