I am running an 18 inch Noveske midlength with the swithblock  1-12 twist.  Accuracy is around .75 MOA with Handloads or Hornady 120gr SST match ammo.  Velocity is around 2667 fps.

The rifle can hold it's own out to 400-500 yards respectably as far as accuracy is concerned and I am pretty happy with this build.

What I don't like is that with the suppressor, the balance is too nose heavy and I don't like the overall length.  The more a shoot and handle the rifle, the more I want a shorter barrel.

I want to send it to ADCO and cut the barrel back  to 14-14.5 inches.

I realize I will be losing some velocity, but what I don't wan to lose is accuracy and bullet stabilization.

Is anyone else running shorter 6.8 barrels with a 1-12 twist.   Less than 16 inches that can give some feedback on accuracy and velocity?

Pics of my rifle as it sits right now.

You do understand you will need an SBR to put it on, right?

try this instead, and keep your current barrel

http://www.faxonfirearms.com/p/38/ar-15-556-nato-145-medium

Having already filled out a bunch of a Form 4's and even the one for the suppressor that is already on this rifle, I'm pretty sure I know and underteand the legality of when it becomes and SBR or not.

The muzzle device on this rifle is a little over 3 inches.    Permanently attaching it to the barrel to bring the overall length above 16 inches does not make it an SBR.

Thanks for suggestion, but that's 556 and my rifle is 6.8.  I also want to keep the switch block.

My question is specifically geared towards anyone running shorter 6.8  barrels and what kind of results they are getting.

I think you have your rifle set up perfectly for what you indicated; good accuracy out to 400 yards+. If you are wanting to cut back the barrel to reduce the front end heaviness due to the can, I believe you'd like the balance of going down to 12.5" over 14.5", however you'd then probably feel like the large scope seems odd for the SBR and consider a 1-4x or even a RDS, which would end up a completely different rifle from where you started. Think about what true purpose you want the rifle to serve and go from there.

I've got a few 68's for different jobs and run cans on all of them, from shooting paper to close quarters hog killing. My target rifle is an 18", and I have a 14.5" and 12.5" for hunting. If you're happy with how the rifle performs at 400 yards and that's your primary use, then maybe she's fine the way she is.

Which can by the way?

A couple of things to consider with your 6.8. IMO, you wouldn't sacrifice very much bullet velocity by cutting the barrel to 16" length.
Also, you could consider changing out the buttstock to something with more weight like a Magpul UBR to achieve the balance and handling characteristics that you are looking for. Personally, I feel that 16" barrel is optimum for a 6.8.
If you prefer to keep your current buttstock configuration, cutting your barrel to 14.5 might very well work for you, but you would have to calculate the loss of velocity and see if it is acceptable for your needs, you might not notice much difference.
And still another option, buy a shorter barrel and sell your 18" barrel. You might find this the most cost effective method.