The "JR Matchbox" with my limited knowledge allows us to save channels by coordinating multiple servos that perform one function. I have dual elevators on my Giles 202, but I need 2 channels to operate the elevator. In my case...one channel is mixed so that the "elevator" movement operates the other servo to the same extents. The "matchbox" (which I've never used by the way) is supposed to allow you to dial in symmetry between mutliple servos and operate them on the same channel...like flaps, spoilers, or on those 35% planes that use 3 servos on the ailerons. It appears the advantage is only when more than two servos are needed.

I am not an expert by any means...I figured out how to use a mix to operate dual elevators...then found documentation on the 8103 that confirmed how to do it. Fortunately there were some special considerations that I was enlightened to such as an "including mix" ...a mix that allows both servos to be operated by the trim button.