Advice on topping

Hey all,
So I'e never topped.
Im more of a set and forget it grower.
But i pretty much always end up with 9 ft tall Christmas trees.
Which is cool.
But in the past I've had branch support issues, blow overs thanks to fucking bullshit hurricanes and mold issues.
So this year I was gonna try to tent them in late sept/oct.
This year I've got three girls. all about 6 ft. Just started to show pistels.
So my questions are and big thanks to all those that answer.

1. Is it to late to top?
2. Will topping cause the main stem to rot?
3. If I top should I also remove some of the lower branches?
4. Does removing branches just as it shows its pistels stress the plants out?

I have never tried topping after flowering has started. It could stunt it more then it helps i at this point but honestly I don't know. I've never heard of topping causing rot. Cutting of the lower branches is something a lot of us indoor growers do to maximize the return from out lights on the good parts of the plant, but if you get your light from the sun, I would live every morsel on them.

I top, or more accurately, I FIM my plants when the are between 4-6 inches.