No I have not tried the Castle XLX. I modify the ICE and EDGE 200 Lite ESC's. The XLX does have more than a standard, looking at pictures its around 2000uF to 2400uF.
My cap bank pictured there is 4x-1000uF Rubycon ZL caps for a total or 4000uF or 4mF. The shunts are always on the negative side of the board close to where the black wire is soldered onto the bus bars. There are two on the top and two on the bottom, they look like black dominos with silver ends. They usually have a marking of "0M50", that stands for a 0.5milliohm shunt.