You can find servos with speeds that are close enough. YOu can use you adjust your endpoints to make them travel the same. I have only done it once before then purchased an 8U and the problem went away.
ORIGINAL: rkramer
So far I haven't read the option of buying a JR servo of the same power and speed as your Futaba. It rotates in the opposite direction making the tail mounted elevator servos act in unison with a simple "Y" cord. Tex.
won't they probably have different travel ranges? (yeah, probably different speeds also, but that isn't usually much of a problem...)