Take SATII tests in the fall or wait until end of junior year?

I’m currently a rising junior. In my sophomore year I took an introductory physics course which covered nearly all of the topics on the SAT II subject test except for thermodynamics. I haven’t taken chemistry yet but I am planning on taking it next year, as well as AP Physics C (both M and E&M - it’s covered in one course).
The three SAT tests I am planning on taking are Math II, Physics, and Chemistry. I was originally planning on taking Math II and Physics in October, and Chemistry in the spring (so it’s not too stressful). I thought I would be super prepared for the SAT Physics test after doing well in the class but after taking a practice test I’m doubtful I could do well on the Physics test without significant preparation - the main issue is finishing the test on time. I’ve also forgotten a few concepts that I need to review.
Another option I would have is to take Math II and Physics on a different date in 2017 spring (May?) and take Chemistry in June, because I’d really rather not take them all on the same day. However, there’s also the question of when I would take the SAT I test, as I am currently preparing for that as well.

For people who have taken AP Physics C and the SAT Physics test, do you feel like Physics C would help on the Physics subject test at all? I’m just trying to figure out if I should prepare to take it in the fall or later on in the year.
Also- I have the official book from ~4 yrs ago when a sibling took the tests, I also have the Princeton Review book from last year, are there any other books that would be really helpful?
Thanks

Wait until the end of your junior year. You will mature as a test taker, more practice tests under your belt, and you will know a substantial amount of math. If you’ve had calculus already, then, maybe its right to take it at the end of 10th grade. Also, when you prepare, check out this guy. It is free somehow.

https://www.youtube.com/watch?v=QkZYp_Rd8NE