basically, the tension is going to be perfect at first (if you did your math right). it's not going to be perfect for long, maybe a few weeks of normal riding and then it's going to be "not perfect but ridable" for a (comparatively) long time until it gets to the point that the chain checker says to replace it.

it'll be safe, you'll just have a somewhat noticeable lag between forward and backward pedaling. it's really not a big deal, it's not going to throw your chain but the sensation can be offputting to some.

so you're either demanding perfect tension and dumping a bunch of money into new chains or you're dealing with "not perfect but rideable" tension.