Personally, if I had one that was to be used for upland with an occasional round of clays, and it was M/F, I'd open them up to at least IC/M, or even C or SK and a LM or M, unless it was to be used exclusively for close birds like grouse or quail over pointers - then it would be C/IC.
A good barrel person can do the job, and usually for less, than having tubes put in