I have always tied down one week prior to flower also. Especially won't hurt yields if you do it during the first two weeks of flower, because that's kind of its "super veg" time. I'm not sure on late flower, but Jorge Cervantez has a nice pic of a beautiful flowering (late) lst in his medical grow bible. All the Nugz were the same size (fat Nugz that all look like those flowers just below the main colas ). So you don't have the crazy thick stems and your yield will also increase.
I'll try to find the pic, but your colas essentially end up spacing themselves apart perfectly along the meristem. They all looked the same size; perfectly uniform.
I would really like to see how this turns out!
I have a hybrid I'm thinking about doing this to. Sativas keep stretching their entire flower! It's annoying
lol. She's a little over six weeks, but started flower sites a whole ten days after the other two into flower, and is still slightly stretching (with calyxes) into week 6.5.
I will say the later into flower, the cell walls of all your stems will be much thicker, and more difficult to tie down without breaking them. But the plant is only redirecting the energy to a different part of the plant. Not much stress or wasted energy, hence the name "low-stress training."