If you are able to kneel at your shooting bench, it will keep you back straight and let you rock with the recoil.
Also, a bag of shot, kitty litter, or a pc of foam board is your friend at the shooting bench.
Love these big bore guns!
First thing needed is to round the sharp edge of the taper to bore on the muzzle.
and get the right ball and patch combination.
A .72 can be from .715 to .730 in bore size.
In my .73, I shoot a mild load of 125FF and a .725RB.