When changing bullet weights and/or velocities in a SXS the POI changes drasticly and at an angle of around 45 to 65 degrees, because the gun travels outward as well as upward, due to the barrels being on the sides.

In an O/U the gun just travels up. The degree of upward travel at the time the bullet exits the barrel determines where the new POI is. If otherwise regulated, the O/U will just move both barrels up, and the POI in relation to this. Say that it is regulated for 286 gr 's traveling at 2,300 fps:
1. A 250 gr at 2420 fps will print low
2. A 320 gr at 2100 fps will print high

In a SXS what happens is:
1. A 250 @ 2420 out of the right barrel prints low and left...out of the left barrel it prints low and right.
2. A 320 @ 2100 out the right barrel prints high and right, while it prints high and left out the left barrel.

Recoil starts as the bullet moves, not as it exits the barrel. That's why smaller faster bullets print lower and big slow ones print high. In the SXS you also have lateral movement to consider.

This is the best rationalization for O/U double rifles. A change in sight elevation brings them back close to target.

Heck...just buy the gun!! Its only money...

Also, I'll put my 412 9,3 dbl on a good scale soon and let you know the weight. Be aware that Tikka made two barrel weights in their 9,3's and other barrels. The most common is the set with a solid rib...heavy. They also made a light version with quarter rib and an improved front sight. I have both and will weigh both for you. I use the solid rib version and have the quarter rib set sold, I think.