This step almost requires a lathe, and as always, start with a scrap piece to check fit.

IMAG0128.jpg
Basic layout

IMAG0126.jpg
I'm still useing the 8.75 adjuster.

IMAG0129.jpg
in the lathe

IMAG0134.jpg
milled 6061 t6 .500 plate, hole pattern in next post. Also, some .100 spacers to replace the drum backing plate.