Competition pilot here. We don't fly Airl to Rudder mix (Airl is the master, rudder is the slave). That mix might be for warbirds or scale personal aircraft like what you'd see at an FBO. It's used mostly for procedure turns. However, that mix will affect so many other manuevers that your Extra 300 is able to do. As an example, most new pilots want to learn a slow roll. With that mix, your plane will have the rudder deflected and cause your tail to wobble in roll. Your roll will look like a snap roll. Or, on an up line if you roll your plane your heading will change because your rudder deflected during the roll. None of the top guys are running that mix.

Airleron differential..... Let me say that the Extra 300 was born to fly aerobatics, an I'm assuming that you are building it to do some kind of freestyle type flying with rolls, loops, spins, 3D, snaps, 4-point rolls, precision flying, etc. After all, if you wanted to just fly around and land, you'd stick with the 4star-60. So off to "aerobatics 101" we go. Differential on this type of plane is used to keep the plane from falling off heading during a full roll, not just a 45 degree bank turn. Here's how to trim out the plane for the proper differential, and so it will help you fly better on all lines (up lines, down lines, straight, and 45 degrees up). Start out with NO differential at all (airleron goes up the same amount as down, measure and get it exact). Get the plane up to speed and pull a radius to a vertical up line, as in going into a hammer head. Be sure the plane is straight up. Do one full roll right , the plane will need a rudder correction to get the nose heading back straight up. Go ahead and give that rudder command and then land. After landing turn the plane on and deflect the airlerons to the right. Take the right airleron and add throw at max deflection , take the left and subtract throw. Add/ Subtract about 5% to start and then retest in the air. Repeat until the plane will roll on a vertical upline without needing any rudder correction to stay on heading. The differential will take away the need to give a rudder correction after rolling. In aerobatics you are looking for the plane to roll, AND ONLY ROLL when the airlerons are put in. Differential allows for roll only.

May I suggest hooking up with a pattern or IMAC style pilot at your local field for other trimming ideas. The above is just one trimming suggestion. There's a lot more to get your new Extra completely "in trim".

Hope this helps, Danny.