Rear hub bolts

[ct]

I need to replace the rear hub bolts on the A. I have steel brake drums so the new bolts require machining as they are made to suite cast iron drums. According to Mac's website the shoulder must be reduced by 1/16 inch.
Questions arising:- (refer to attached photos)
1) Is the taper between points A and B an integral factor in the swedging process?
2) Does the taper need to be maintained or can the shoulder be squared-off?
3) If it can be squared-off, from which point is the 1/16" reduction measured?
4) Has anyone worked with a dimension (C) that the shoulder needs to be from the drum pre the swedging process?
Thanks in anticipation of your responses. CT