one short and one long speaker cable work?

I think Geoff is saying the sound between the two cables will be inperceivable. A typical speaker cable with low impedance will not have an audible difference between such short lengths. 

Keep your cables as is and dont coil them.

You could always go to a local hardware store and pick up 8M of wire and cut it into a 2M and 6M lengths and try to hear a difference between your AQ's at equal length. Listen for imaging and soundstage not the differences in tonality.

Cables should always be the same size.

How about two different brands of the same length, conductor metal and gauge? Is that a no no?

@geoffkait .
I don't think it would damage anything, but knowing that different brands have different sound qualities, why bother?
The question the OP posed was whether it wise to use unequal lengths.
Where's Almarg when we need him?
B