mechanically you can do it but one servo would have to be mounted two widths of servo arms higher then the other so that makes physical placement extremely difficult. The simplest method is to have the servo reverser cable. The best method is to have a computer radio with sufficient mixing capability. I say suffcient because anything less then a futaba 9c just does not have advanced enough software for what you want to do. Sorry If I do not mention Jr or other brands but I am not familiar with any other brands enough to recommend. You have to creat linkages that are as close to the same length as possible for the servos or else you will get uneven movement. The computer mixing is best because you can incrementally computer trim the different sides so that the are even instead of trying to mechanically get them just close enough which you origianlly do before you computer fine tune them. THe 6exa and 7c are decent radios but you can not gang trim both servos in flight so you create a roll condition