Too late for topping?

If they are autoflowers, i wouldn't top after 4 weeks.. if it is a photoperiod, you are fine to top after 5 nodes are present as much as you want as long as you havent initiated flowering cycle yet

It is almost never too late to top photoperiod plants, but it is best to not top autos at all.

High Heckenpflanzen, No you do not top autoflowers because they do not have enough time to recover from it. You want to use LST and with this method you bend the plant in a shape that you want to archieve. You try to let all the larger buds grow on the same height and distance from the lamp. This is the best way to train an autoflowering plant and will give you the best results. What you want to archieve is to create a screen full of green. That means that when you look at the plants from above that you do not see the floor from the tent. This way your plants are getting the light from your lamp as efficient as possible and will give the best results and ratio grams per used wattage. Happy Growing Buddy! 💚

Would say not too late by plant size, but you grow autos , so NO, better do not do it. There is plenty other ways yo manipulate plant.