Okay, I have my blank planed square on two sides, and have set up my centerline to take into account a cheekpiece.

Now I want to figure out cast offset for a right hand shooter.

Is there a forumula for how much the center of each of the screw holes (top and bottom) should be from the centerline of the stock, or is it just a matter of trial and error for each individual shooter.

Also, is there a standard place from where this offset starts from. Does one start from the back action screw, or from the comb, or from somewhere behind the comb, to make this offset.

blue

There can be no set dimension for castoff. To say there was would be like saying a size 10 is the ideal shoe. It might work for some but I'd be in a lot of pain! A person's whoulder width, facial structure, shooting style, neck length are just some of the things which influence the amount of cast off or whether there should be any at all.
I require none and can in fact live with a stock which is cast on a bit. I think cast off should start right behind the tang.
By the way, one of the finest stockmakers I know thinks most stocks should be straight with comb width being the only variation. Regards, Bill.

Cast off should start at the grip behind the tang..I like about 5/16 or more....

Cast off is wonderfull in heavy kicking calibers and especially on double rifles..

My pattern stocks have just the right amount of cast off for me, and that saves me from having to worry about getting it right from stock to stock, or rather the same on each stock, as I have found it a little tricky to keep the grip right and still getting that minute of cast in the taper, it would be easy to over do it at that juncture unless you have done enough of them to live my muscle memory like some stockmakers..