Yea, I forgot the part about the 1.5 x .120 option going away (also I ignored the older option of using a thinner/smaller tubing if it was chrome moly). On your STU question, it depends on whether you'd be required to have a different logbook for running the car in another class. I've never seen anything that specifically addresses such a change. And I do have a real life example where I'm using the old ITB logbook for a car that has been converted to FP. But I'm not sure if this might be an oversight by tech, or it is in fact the way the rule is supposed to be interpreted (i.e., no new logbook required). But in my particular case, the cage rules are the same for both classes, so I'm legal either way.