I didnt have any thing to go by so i made the internal diameter 1". I was afraid to make it smaller for fear of snagging the wads. I found the wads from todays testing and they didnt show any evidence of contacting the gills on the comp. Next up i will check the pattern for birdshot and buckshot and also make sure it doesnt affect slug accuracy. And,yes, i will be able to change chokes w/o removing the comp. Im in the process of making an extended choke wrench.