The simplest way to connect two servos is using a Y harness plugged into the normal aileron socket on the Rx. Doing it this way will mean that you don't need to worry about getting the connections reversed (very bad, trust me) however you will need to ensure that the mechanical connection between the servo and the aileron is such that the ailerons move in opposite directions.

The alternative is to use separate channels and mixing. I assume a 9CHP is a computer radio so you should be able to do this, the advantage is that you will be able to use flaperons. All in all I would leave this until later.

Usual way to balance a prop is to carefully remove a little material from tip of the heavy blade. Never heard of anyone adding weight, getting it to stay attached would be a challenge[X(]

Regards


Terry