Rifles standing straight up, or close to straight up, have no problem at all with weight distribution. Obviously, as the gun is stored at more and more of an angle, (i.e. the butt is moved farther out from under the muzzle) there is more strain applied to the weakest area of the gun, i.e. its wrist. You did not mention the weight of your gun, whether a lighter buck-and-ball type vs. a heavy barreled rifle, or even a heavy vs. light weight rifle, which probably plays into the equation...as does the heft of the stock in the wrist area.
While I do not know if the 17 inches out of line will eventually stress and possibly hurt your rifle, it's always better not to take chances with antique guns, even if in good, solid conditon. I'd suggest turning the gun over, presuming it will fit in the gun safe that way, so the muzzle is down and the hammer area may then contact the safe wall, and perhaps the butt lightly above it, to minimize stress on the wrist area.
The risk from storing the gun at an angle with muzzle up and wrist unsupported might not be as much from long term stress, as it is the more exposed condition that is more prone to crack or break if an accident occurs. In that position, if the gun is accidently hit by another gun, or something is dropped against it, the wrist is unsupported, stressed, and more prone to damage from impact than if stored differently. Shelby Gallien