Empirate
First Post
This is the most important thing, right here. CRs are mostly just a guess and compare game. On the plus side, CR guessing is a pretty forgiving hobby, so if you are off by a CR or two either way, it should not affect play much.
Forgiving hobby? You obviously err on the side of caution when estimating a monster's power, and I commend you for it. But if you think along the lines of "well, this monster is about CR 7, my 4th level group should be able to handle it as a bossfight", and your CR is off by 2 in the wrong direction, you might have a TPK on your hands.