Unfortunately this was designed before the E3D v6 was around, so it fits the v5. Not sure if the coupler will fix the problem, but I would suggest going low tech and back to the rubber hose and zip tie for a trial. It really isn't a bad setup if you bottom out the Z thread on the motor shaft.
You could always raise your bed by adding shims or spacers with longer screws, or stack some cardboard under whatever you are using for your print surface. You will loose some Z height, but it will make up the distance to the hot end.
Another option is to buy a v5 heat sink which is longer than the v6. I believe the heatbreak is the same thread for both versions and this will give you the extra length needed.
Maybe somebody else can confirm if the coupling will get you where you want to go. Good luck.