Photoperiod plants can double or triple in height after the flip, and that stretch varies widely between feminized lines. A sativa leaning strain in a low tent ends up pressed against the light with burnt tops, which is a frustrating way to waste a good seed. Stretch ratings for common feminized strains, sorted by expected growth after flowering starts, are listed at https://queenfeminizedseeds.com to help match genetics to available headroom. Measure your tent before choosing, not after.