As NE450no2 so kindly noted in a prior post I morphed to the present one starting with a similar charge for a heavier bullet and working up the same charge for a lighter similar bullet should work without pressure problems in a Double.
Great idea and a great place to start when shooting a lighter bullet and save a lot of time!!

It seems that regulating a scoped Double is a whole different game than a bolt.In the bolt you shot the bullet then adjusted the scope to "move" the bullet, but you are just chasing the bullet in reverse.Do that in a Double at distance you could get screwed cause you will have one barrel hitting one barrels scoped POI and the other barrel possibly way off for that short range regulated load.Ideally a great regulated load at distance should work at close range but not necessarily the reverse.
Am I correct here or confused??

In a Double shot at distance it would seems you want to get the crosshairs where the fixed sights aim and then possibly adjust that cross hair a fixed amount depending on the flight path of the bullet for a zero at distance.In reality you are raising each barrel POI to hit spot on at some distance. For a 500NE 100 yds the bullet fall is 1.2 inches above the POI of each barrel at 50 yds, an insignifigant amount.For higher velocity rounds at further distances more elevation would need to be dialed in.This assumes the scope is taken off at closer ranges for iron sights or POI varies.
You would have both options like a bolt gun with fixed sightsand a long range scope.

The better and easier alternative surely seems to leave the crosshairs at the zero distance and holdover the target an appropriate amount!!!

Am I correct here or flawed in my thinking??