Double rifle regulation is art rather than science. The additional weight and stresses could affect the interaction between the barrels. However, starting with a rifle which you know will regulate (which this one apparently does - or did) helps a lot. I would suspect that the regulation load will stay pretty close with a scope. My one caution is with regard to who did the QD mounts and what sort are they? If they required soldering, like claw mounts, then heat was applied to the barrel joint and regulation could have been affected. The mount builder should have rechecked the rifle with whatever load the owner was using. If some sort of shade tree gunsmith mounting solution, then heaven knows. I would also note, that unless you have that exact factory test load (to include the particular production run of that load), you will likely be searching for the perfect match in any case.
