I've often bored hard jaws 'straight'. Straight is a relative term, because you have to consider preloading the jaws at various pressures will affect the amount of deflection. Make up some kind of a heavy ring with allen caps or something to fit in the bolt holes of the jaws so you can close the chuck jaws against this rig.
I prefer a bored jaw for a hard jaw that will be used in roughing as the scallop effect of the tool marks creates more gripping power than a ground surface. Use something like a 1.5" boring bar and a carbide insert at moderate rpms, and a fairly coarse feed and of course, take a light cut. The insert should live long enough to make it all the way from front to back. You might even consider using an old TNMG insert, grind the chipbreaker off to make a nice sharp edge. The honed edge of a new insert does not cut quite as accurately on hard stuff because the depth of cut is so shallow.
BTW, most chucks can be bored out. One thing you'd want to check is how deep the pinion gears seat into the chuck because you'd not want to be boring the chuck out only to expose the end of the pinion bores. But I bored 1/2" out of a 12" Rohm to make it swallow 4.125
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)