Great discussion here.
But cutting to the chase, with quality bullets and barrels, a bit more twist than needed hurts less than having not quite enough.
Greenhill works well in our cast bullet situations, with blunt bullets at lower velocities less than 2000 fps.
With subsonic loads a faster twist helps.
With the highest velocity which is usually practical with cast bullets, over 2000 fps, then a slower twist helps.
But, if the barrel is good, the bullets are good and your load is well-balanced for the alloy and caliber, much of our twist discussions are mental masturbation.
My most accurate cast bullet rifle is an Obermeyer 5R with 13.7" twist in 7.62x39 which I shoot 190-grain cast in about 1800 fps.
My 14" twist .30-'06 is also wonderful with #311299 and heavy charges over 2000 fps.
But I also have a 7.8" twist .30-'06 which stabilizes 240-grain bullets at the lowest velocity which exits the barrel and is little louder than a .22 LR firing standard velocity match ammo.
My favorite woodchuck rifle is a 7" twist .22-250 which is 1/2 moa with Sierra 53-grain HP benchrest bullets and 36 grs. of 4064. Bullets leave a blue smoke trace and do not exit a 200-yard woodchuck, but inflate them like a ballon, leaving 2 quarts of strawberry jam in a leather bag.
Joe and Ric are right. Take care of your good barrel.
Be fussy in visual inspection of your bullets. Weighing matters only to discard obvious outliers.
Have fun. Don't over-think the problem.
73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia