Window motors in parallel

[JellyMan]

Thanks for the fast replies!
The FP motor (#0673) and gearbox was our first choice for the lifting arm, but only one FP came in the 2011 KOP, and we already allocated that FP motor to an elevator function. We have two FP motors (#9015) and gearboxes from our rookie 2010 KOP, but the Andy Mark website lists the 9015 motors as illegal for 2011. Any idea why?
We are still essentially rookies in experience and resources of all kinds (especially funding), so we are stuck trying to make do with the scraps we have. We'd like very much to make use of the 2010 FP motors.