Al, thank you. I have been using this table out of context, and have not been referring to the text first.
But, this is still confusing; Table 4.12 says to see clause 4.19, which simpy says that changes beyond the variables given in Table 4.12 shall require re-qualification.
But then if you read the very next clause (4.20), it shoots this whole thing down in the first paragraph.
Gotta love the "farm code"