Willy:

If you have a programmer to match the pair acurrately they'll work. Matching includes the angles at several different pulse widths. Any mismatch will result in one servo fighting the other, and running your battery dead. It's just safest to have a complete match, including brand and type.

Your airplane. Your money. Do as you wish.

Go ahead, run your battery flat.
. Your plane'll go in, and that is that.

Bill.