JR 622 and Elevon's again
Just tried that out here, it looks like it works to me if you wish to do it this way. I believe what you are seeing is the servo reaching the end of its travel in one direction with down elevator or up elevator. One servo will run out of travel when you give it down elevator, and the other will run out of travel when you give it up elevator when combined with the aileron. You will notice the same thing when you give it full left or right aileron and move the elevator, that one or the other servos will stop. This also can happen with standard elevon mixing, so it looks like it works just fine. You do also need to zero out the flap travel to stop the switch from moving the servos, and also to keep both servos centered properly.