You didn't give the weight or objective lens diameter of the scope, but I think your gunsmith made a good point. Hard kicking rifles, like a .30-.378 Weatherby, put a lot of stress on scope mounts. The bigger and heavier the scope, the more stress on the base and rings.
Think of recoil force like the acceleration force of a pickup. If you're carrying something in the truck bed, when you accelerate, the cargo will slide towards the back of the truck bed. What's going to hit your tailgate with more force: a 50 lb sack of dog food, or an upright piano? The piano's a lot heavier and more likely to break your tailgate if you punch the accelerator. Same goes for big, heavy scopes.
You don't see 4-12X50mm scopes on big-bore, dangerous game rifles. There's a reason for that. It's your rifle; you can do what you like. But don't be too surprised that you have to beef up the scope mounts (the gunsmith should have pointed that out to begin with).