It's telling that most factory smoothbore slug guns are either Cyl or IC. Either fixed choke or in the removable choke that is shipped with the gun. I expect some testing was done there for accuracy.
I use IC in my 870's and 11-87. I have a Mossberg Cyl slug barrel that I rarely use. I have shot them through Modified and Full chokes with no damage, but that's about as much as I can say for the experience. Best accuracy I've had was with IC.