I agree with you on the .40 caliber in both rifle and pistol. I have built more guns of that caliber than any other.
Yes, learning to use a target shooters stance instead of a hunters stance takes quite a bit of practice. When I was very young I found out what the design of the Bethlehem style was made for.
That was my very first longrifle. The stock had extreme drop to the butt and a short length of pull. In combination with a pronounced arc to the buttplate forced me to hold the rifle in a target shooting position. That is, head vertical for best body balance, sideways to the target and with my elbow vertically under the forestock.
If you observe Olympic shooters in position you can see what I am talking about.
Most "modern" shooters learn to shoot in a modified shotgunners stance which is quite different. If you get behind one and observe you will notice they are leaning into the gun, head bent over at an angle and body about 30 to 45 degrees angled to the target. That is a good position for moving targets but not so much for one that is stationary.
Since you have an interest in the southern style of rifle go ahead and grab one. I think you will surprise yourself how comfortable they are to shoot when you get used to the different method of holding a rifle. Yes, I know the different style of shooting is difficult to change to after shooting for 50 years in the hunting style of offhand shooting.
May your shots be all 10x !
Barry