How big is the sweet spot for the vandersteen quatro wood CT speakers?

Just fell in love and purchased a pair of Vandersteen Quatro Wood CT speakers. Going to be set up in my living room approximately 13 x21. The speakers will be 13 ft apart. We'll have two chairs. Our heads will be 6 ft apart  and 18 ft from the speakers. Has anyone had any success creating a sweet spot  that wide (so 2 people are in it)?
I would just call Richard, he answers the phone

read the manual and try to follow the extensive setup advice before you call

Also buy a small level laser it will help you with aiming
your 13’ dimension seems to infer you have them stuffed in the short wall corners..... see if you can relax that a bit....
If you've put the Quattro's deep into the short side corners (along the 13 foot dimension), try moving them out of those corners, a few feet from sides and at least a foot from the back wall. "Sweet spot" is fairly wide, laterally, with Vandersteens, but in my experience sound is a lot more focused when you're sitting down (not standing) in the "zone." The Vandersteen rear-firing tweeter (if turned on) helps ameliorate this problem somewhat. Good luck, and don't be afraid to experiment with speaker and listener position.  
I own a pair of Quatro Ct's myself.  Very enjoyable speakers!
Will your dealer be doing the setup?  If so they should have the tools necessary to dial in the speaker.  I think the sweet spot of the Quatro is less sensitive to lateral positioning than it is to vertical.  Also, don't be too prescriptive in the placement of the speakers and/or listening chairs.  The optimal listening position (sweetspot) is usually a function of all of the conditions that you seem to have pre-determined.  Be flexible...
Thanks for all your input and suggestions. John at audio connection in Verona New Jersey will be doing the install. From what I've read on the internet there shouldn't be any problem, he's very qualified
+1 for Johnny R.
I have no doubt you will have it set up properly.

For me, with my challenging room. I find the 'sweet spot' fairly large and 2 people can listen easily. FWIW, I like to move around and am often out of the 'sweet spot'. I like it just as much, which is why I love Vandersteen so much. It always sounds good.
+2 for Johnny R
Agree w gdnrbob, my Vandy 2Cs have an amazing sweet spot
Not sure about the Quatro but on my 2CE Sig II, the sweet spot is only 6”
Oh...Johnny R is doing the setup. Your in awesome hands.  I had a very challenging setup and Johnny spent like a hour setting up my Vandersteen Treo CTs and boy do they sound great.  Seat back watch the show and afterwards listen to the magic. 
Thanks for all your feedback. John is amazing. Came and scoped out my living room and we decided to put the amp in the basement so it wouldn't be that far away from the speakers. We even checked to make sure the amp and preamp would be on the same split on the breaker box. Talk about being thorough. Can't wait for the speakers to come in
@OP, are you going to leave the amp on continuously?
@miketuason ,
If your 'sweetspot' is only 6 inches, I think you need to do some adjusting.
The amp will turn on when I turn on the preamp. The chairs are set so our heads will be 6 feet Apartment 6 in
Bob my speakers are pretty well placed and set according to the owners manual and actually, that’s what the spec says IIRC only 6” window,  I wish it was more than that.
+100 On Johnny Rutan.  A true pro.
The 6” window is with respect to vertical distance. The horizontal “sweet spot” is actually pretty wide as the horizontal off-axis response is quite consistent and smooth. 
@miketuason ,
If I were you, I would try moving the speakers. Sometimes the formulas don't work and placing where the 'rules' say no, may make a difference.
If you can find a Vandy dealer nearby, or call Johnny at Audioconnection,  you'll get more information for free than you can imagine.