Don't remember the brand of the one I fitted but it was larch which is one of the better conifer timbers.
Also pretty sure that hatch kit was up to 2.8m and our ceiling is more like 2.2m. And I did make sure to cut the two movable steps rather than making the end one extra short. A bit more work and your have to be somewhat precise but like this it folds much better than similar I have seen where only the bottom end was cut and the bottom segment ended up really short.
However, of at all possible I would seriously look if a wider one is possible. So, for example, 900mm rather than 700mm.
I'm my case it wasn't due to the joists and the coving in the hall. But since then, whenever I try to move anything large in or out of the loft I say to myself "if only this hatch was wider".