I have built a few double rifles and I have built and regulated them for scopes as my eyesight it not as good as it was 70 years ago. However, the vast majority of double rifles, including o/u's were not regulated at the factory using scopes. Most double rifles are regulated at the factory for 50 yards/meters.
I prefer the super lightweight Leupold scopes and I cannot determine if your scope is one of them or not, nor can I determine from the photo if your beautiful superposed has iron sights. The weight of the scope, its rings and mounts plus the weight of the scope, will make a double rifle original regulation go astray. If you have iron sights I suggest you determine which 30-06 loads work best for your double rifle at 50 yards and then from there determine how to make your double rifle shoot where you want it with the scope.
On the double rifles I build, I machine the scope mounting slots into the rib in order to reduce the weight and this helps a great deal in shot regulation. You may need to reduce the weight of your rings and mounts by trying ones made of aluminum.
In general for the issue you have, slowing the speed of the projectile will lower the shot at the target and you may need to hand load your ammo if you do nothing else to the scope or mounts.
Double rifles can be very accurate and the ones I have built will place the shots touching or nearly touching each other at 100 yards. However it sometimes takes me several weeks of work soldering and de-soldering the barrels at the muzzle to regulate them to where I want to shoot with the load that I want.
I live a hour or so from you and if you want to talk to me about your double rifle targeting, you can PM me and I will give you my telephone number.
Kindest Regards;
Stephen
