I find TN manipulation to be okay for an uncommon Sidereal manipulation. However, aside from that I think variable TN should be avoided at all cost.

Personally, I don't have any problems with math and juggling numbers. So I also don't have any problems with all the old systems created by engineers (I think Phoenix Command is a nice little system).

The thing is, most isn't engineering minded, and fast calculation in the head is hard for many. With the StoryTeller system, I might still think 4+3+2+2 dice is 11 dices. Someone that isn't just have to pick up four, then three,...