I used to hunt with patched round ball, and one of my long term goals in life is to get back to it. I have a .54 TC Hawken, and I have the original barrel that was meant for round ball as well as a Green Mountain IBC barrel for shooting conicals. I've tried the reverse-- shooting round ball out of the 1-in-28 Green Mountain barrel, and it's not pretty.
The problem with modern inlines is they generally have too tight of a twist for patched round ball. I don't know if it's too much spin or that the patch gets ripped out of the rifling or what, but I never got good accuracy out of that combination. 40 yard accuracy was iffy at best, but then that was about how bad Maxi-balls were out of the round ball barrel.