Do you know what "FIM" is? it means "fuck I missed" method of topping. perfection is not needed.U don't need to worry boutt makiin a precise cut at all. Just cut a couple tops off (few inches atleast if u wanna make clones) or just pinch off 3/4 of a new growth. No need to precise at all. I've accidently topped couple plants when I supercroppingg and they grew just as fine as ones I took my time topping.