Ok, so I have gotten all of the bugs worked out of my newly purchased 2003 260. Although a pain in the a$$ chasing issues, it has helped me learn alot about the boat (stuff I wouldn't have learned had I bought a perfectly running boat). I am still learning the 496 mag and Bravo (all of my previous experience is with carbed small blocks and alpha drives).....
Anyway with that said I am now looking for advise as to what is the best RPM to run the 496 mag to get the best fuel economy and least amount of stress on the motor. What RPM do you guys "cruise" at with the 496 mag? Is there a "suggested" cruise speed/RPM provided by Mercury and/or Velocity?

You need to size the prop so that your engine will reach at least 4600rpm wot with a full load. This should put it at around 4800rpm with a normal load and no more than 5000rpm with a real light light load. If the engine has too big of a prop it will "lug" and that can damage it. I believe you already know from your testing what size prop is best: 26p B1, 25p QIV or labbed 26p QIV. A 5 blade will give you the best cruise speed with a little off the top; I would guess a 24p or 25p Hydro P5-X, but they are big $$. In your shoes I'd send that 26p QIV out for a tweeking to gain 200rpm...

A good cruise speed would be anywhere between 2800 and 4200 RPM; what ever the water conditions dictate. You have EFI not a carb, so no secondaries to worry about...