Your absolutely correct "Jeffs" and at most times when the rudders “kick up” you are not really concerned about your sailing speed as it’s mostly about saving your rudders from breakage from hitting something “solid”. Even if they kick up from dragging large amounts of weed, you still want them up to get that weed off of them. As I said the only time that having T foils on “kick up” rudders is a real “pain” is when you have to sail out off the beach with them half way up/down, then there is a lot of drag that can be problematic.
With the T foils in “cassette” type stocks everything works great all the time, with the possible exception of hitting something really solid with them down – but then we have used them now for some three plus seasons and never broken any while sailing (and they have hit bottom rather hard a few times)