A little test, 2 strech upper horn.
 

Guys,
I think there will be no need to stretch the upper horn and to destroy the design. The single DW balances more than perfect, and with two options of back strap pins and the bigger lower horn (much bigger than the normal DW lower horn to fit the master vol and pu selector) there will be no need in doing this. It WILL balance perfectly, believe me.....
 
Oliver (Spyderman)

If not. Here are a couple of renderings of the two different shapes.  

 

Rob,
sorry, as said before. Looks not good and destroys the design.
Just my opinion.
Plse leave it as is.....
Oliver (Spyderman)

OK. It's your bass.
How do you like the logo on the pickups?

Rob,
well, you are getting better and better, or better said: PERFECT!
Is the different shine on the strings kind of a shadow thing?
 
Oliver (Spyderman)

Nope. It's a strange graphic error only visible when I render with perspective.