Sounds good. See what happens at 70, and if you feel you're losing more FC than you should be, try 80. Either is fine. Another one of those things you'll learn about your pool.
It's OK to experiment with your FC/CYA levels, as long as you're not way out of range. Remember, TFP numbers are guidelines, and can and should be tweaked if conditions demand it. For example, if you have your CYA at 70 and consistently maintain FC at 5, but once in a while see a little tinge of green on one of your walls, then you should goose your FC a bit. Maybe in your pool one or more of the variables I listed is consuming extra chlorine. So you adapt. Others might want to see how low they can run their FC, perhaps because of a skin sensitivity. So they might run their FC closer to the minimum, but test more often so that they don't drop below it. I don't like taking chances with algae and I have a lot of kids in the pool, so I run my FC a bit higher than recommended. The correct FC level is what's correct for you and your pool, and that may or may not be exactly what TFP recommends.