That's not entirely the case, the cheap 4-channel Giant Shark transmitters mix at 100%. And I've bought an external mixer in the past that mixes at 50% fwd/back. The Giant Shark mixer linked above is cheap but I've had situations in the past where they cut out if when the stick is pushed right to the diagonal (an action that should normally just make one wheel turn). On all occasions they've been used with Botbitz controllers though so I suspect it may a problem similar to the mixing issue with the DX6i and TZ85s. Haven't tried the mixer with a different brand of speed controller - probably should to confirm the issue.

An external mixer I've had no problems with is this one: http://www.hobbystores.co.uk/default...:0,c:070,b:GWS
It's slightly more expensive but guaranteed to do the job.

If you don't want the fancy 6-channel controller from Giant Shark, the cheaper 4-channel one I mentioned has mixing: http://www.giantshark.co.uk/product/...e2-transmitter

It's worth mentioning though that the Giant Shark receivers can have problems connecting to the transmitter when you're trying to arm up at the same time as 15-20 other featherweights. They just seem to get flooded with all the other 2.4Ghz signals flying around.