Karybouhanswered grow question 4 years ago Grow: 40-60 cm(16"- 23")
Flower: 30-40 cm (12"-16")
Always measure from top of the plant otherwise you will burn it, try to keep the canopy at same level(LST,top, according you grow), as you don't have mylar walls you can go a bit lower.
If was me, with same installation will put it 20" and even lower if going tall.