I can almost guarantee a 28" varmint contour barrel is going to balance HORRIBLY in the MDT LSS chassis; you are asking a short, lightweight chassis to work with a long, heavy barrel...that's no bueno IMO.

Besides, you don't need that long a barrel to reach 1000yd comfortably; there's a guy on Snipershide getting 2690fps with 130gr Bergers through a 16.5" 6.5x47...