A factory Remington 700 XCR in 7mag, 300Win 8.25 pounds scoped with a 3.5-10x40 Leupold?
If you can afford a guided elk hunt
can't you also afford a rifle and scope well suited to the job/terrain?
Why not bring a rifle, scope, and bullet that performs comfortably from 0-350+ yards?
Also I would ask him how many 350+ yard shots have been taken and exactly how far those shots were.
My custom built 300Win and 338Edge rifles are capable of much farther than 350 yards with their 2.5-10X Nightforce scopes and they only weigh 8.5 and 8 pounds 10 ounces respectively. They could be made to weigh less if you really felt you needed that (I would not advise that with the 338 Edge).
The 300Win with a 200 Accubond/TSX makes a sensible do most Elk combinations without creating a lot of recoil at 8.5 pounds.