I tried on my iA6 and decided I would rather be flying so I grabbed a "V" tail mixer and said "Stuff It" to trying to fight the programming to get what I wanted.
HAPPY NEW YEAR!!!!!!!!!!!!!!!!!!!!!
I had never heard of the "V-Tail Mixer" until you posted about it. After looking it up that seems like a decent way to go if you just want to get it in the air without trying to wrap your head around the programming. It looks like it would be about the same weight as a servo extension, and it's only a few dollars.
On the other hand, I found it pretty simple to get my Sparrow flying right using the mixing in the FS-i6. The i6s is a little different though in that it only has one mix available, and that the user decides which channels mix. In some ways it looks a little easier to set up, to be honest, since you can just tell it to mix (like channels 1 and 2 for elevon mixing). And if the control surfaces are moving in the wrong direction you could reverse them, or just swap the channels that the servos are plugged into.
In my case with the i6: the Sparrow has a V-Tail, and so you would think the V-Tail mix would do the trick. The problem is that the V-Tail mix in the i6 didn't give me the correct controls (2-4). After some trial and error I discovered that the Elevon mix (1-2)was what I really needed, and with it set up that way it flies beautifully. I had some time to figure this out, and by the next day the only problems I had controlling the plane were due to my lack of skill.
If I had the i6s I would take the time to learn how to program it. One of the reasons to have a capable radio is so that you don't have to use workarounds to make things function. I also like tinkering.