Smokey,
You have gotten a lot of opinions so far. So I don't expect you to lose any sleep over mine.
I am very skeptical about a lot of what is passed as definitive fact about what was done in the old days. I have never seen any reference to a short starter in historical writings or surviving accoutrements. But I don't think the old-time hunters loaded their rifles the way we do, nor did they use them the way we do.
The need for a short starter comes from the need for a tight load. The need for a tight load comes from the need for accuracy out the rifle with a relatively fast twist. John Getz made the barrel for my 54 with a 1 in 72 twist and radius grooves. I shoot 85 grains of FFFg Goex a .520 ball and .024 denim patch. I start the loads with my thumb. I don't own a short starter. The rifle shoots better than I can. MY eyes have gotten "old" (no comments about the rest of my body, please) so sights and trigger are far more important for accuracy. Off-hand I can hold 2.5 inches at 75 yards. My preferred shot for deer is right behind the eye.
If you need to cone the barrel to get your load down the barrel then do it. Odds are that you will not notice any loss of accuracy if you are shooting off-hand. I certainly won't!
Keep in mind that the old-timers lived in a different world than we do. When a gunsmith had finished a rifle he went into the house, snatched a piece of the cloth his wife purchased from the itinerant peddler who passed by last week, went to the shop and started turning a cherry to make a mold. When the lollipop of steel he was using for the cherry fit the bore of the gun while wrapped in some of that cloth he stopped turning it smaller, cut cutting edges on it and case hardened the cherry. Then he made the mold.
I don't think they used the tight loads we use nowadays. Their powder burned more slowly so they could get by with the ball patch combination they had available. They had their share of misses - but nobody bothered to record them. I shared a camp with my friend, Greg, one fall. While sitting around, he took his .22 pistol and started throwing a quarter into the air and shooting at it. After I don't remember how many tries he hit the quarter. I still have it! Greg said that nobody very remembers how many time he missed, only the time he hit. He is right!
Build your rifle. Cone it if you want. Enjoy it - life is too short.
Best Regards,
JMC
John Cholin