Longtime lurker first time poster.
In Canada this is strictly not allowed. Conductors smaller than 1/0 can only be run in Parallel if they are in the same cable. COnductors 1/0 and larger can only be run in parallel if they are (among other things) of the same length and free of splices. (see rule 4-108 of the CEC if you are interested)
The issue that I see is that if you have conductors of different lengths, you have different impedances. Different impedances lead to potential phase differences at the load (i.e. where the conductors join back together) and the potential for overvoltage at the motor. At the very least you should ensure that the conductors are of the same length.
Steve
