The best position is the one that you can get an acceptable installation in. If you can get a good install in the center, then install it in the center position as that is statistically the safest position. If you cannot get an acceptable install in the center, the outboard spots are still safe.
Try each position with both the lower anchors and the seat belt. Install them seperately; not with both methods. You cannot use both LATCH and seat belt at the same time, but sometimes one method will give you a better install than the other method, which is why I recommend trying both methods. Whichever one works, use that. :thumbsup:
If you are installing with the lower anchors, please note that your LATCH weight limit is 48lbs, so when your child reaches 48lbs, you must switch to a seat belt install (which since your True Fit only goes to 35lbs rear facing, your child will already be forward facing when you have to worry about that). Don't worry though -- seat belt and lower anchors are equally safe.
As far as the center position, you can use LATCH as long as you do NOT have other car seats attached to the same anchor. You can only have one LATCH connector per each anchor. Does that make sense? So if you install the True Fit into the center spot with LATCH, you can only install other car seats in the outer positions with the seat belt.
Will you have other children riding with you?
Anyway, whichever spot gives you the best install is the one you should use. :thumbsup: