According the Jayco web site a 2010 256RKS has a GVWR of 7,350 lbs., UVW of 5,570, and dry tongue weight of 625lbs. If you loaded this TT up to it's GVWR, the loaded tongue weight range would be 735lbs to 1,102lbs (10% to 15% of GVWR). A visit to the local CAT scale (or Sherline tongue scale) would confirm your actual loaded tongue weight.
Make sure you confirm which "version" of the Reese HP Dual Cam you have, there are two versions and they both have different installation instructions, set-up dimensions, and component assembly. What makes it even more confusing is that the Reese model number (26002) is the same for both versions. With 1,400lb rating, it must be the trunnion style spring bars.
Early Version (gold in color): http://www.truckspring.com/Installat...eese/26002.pdf
Latest Version (2010, silver in color): http://www.reeseprod.com/content/dow...ion/N26002.pdf
Ideally you want the spring bar rating no less than the loaded tongue weight, but to high of a rating makes adjusting the WD a little more challenging and can make for a "stiff" (no give) WD connection.
I agree with your earlier statement that the 800lb bars may be on the lite side (2-6V, larger LP, etc.), and IMO a 1,000lb rated bar would be ideal, and a 1,200lb rated bar would be for worst case loaded TT weight. All depends on how heavy you load your TT.
Also confirm that there isn't any WD limit restriction tag on the TT A-frame, I believe Jayco has them on some units.
Just thinking out loud.