Double run of speaker cables?

This would be feasible if cables were "shotgun" (non bi-wire) configuration. Don't see how to do it with bi-wire cables.

I have run "shotgunned" biwire cable configurations before when the biwire was not of sufficient gauge but  I eventually replaced them with a larger gauge biwire cable. By all means try it and go with whichever way sounds best.  

I experimented using 2 of the same cable to double up for a while and have now switched to a heavier 10 guage ofc copper cable with similar jumpers.  I think the 10 gauge sounds better, time will tell. 

And, you would get yet another result if you tried doubling the 10 AWG speaker cables in place of the jumpers. You cannot presume you have found the best alternative until you actually compare. However, having done some cable switches, you may be content. Nothing wrong with that.  :)