I have seen mainlining done with autos as well but your timing has to be perfect.
Yes using clones it’s harder to mainline for sure. The whole point of it is to distribute nutrients more evenly but with your node spacing it won’t be so even. I would also take the advice of aqua man and wait to top that clone. Give it a little more time and then I would probably top above the 4th node and remove bottom 2 nodes to create the mainline. It may require a little more training to get them as even as possible but you can do it. Next time you want to do a mainline or manifold start with a photo seed you won’t run into node spacing issues.
Thankyou for the advice ! Well I don't have to try mainling if its gonna be too difficult for my first time, as these are cuttings, not from seed, they are photos not autos, last time I used a scrog and it all went great, I just fancied trying to learn something new, that's all pal, but sounds a bit more difficult than first anticipated and last thing I want to do is screw it up