You need 2/3 of the states for a convention. But you need 3/4 of the states to ratify.

Thing is, though, Constitution is just a piece of paper, if enough people - or states - believe that it is. Small states need to understand that the power that they wield is theirs only because the large states agree to abide by this arrangement. If that power is abused too much, the deal might just be altered - and in any such alteration, the larger and more powerful states will call the shots.

But they won't, and that's the beauty of the way it was set up. Every state still gets two votes in the Senate, and you can't change that without an amendment.

The majority of the small states still have to sign off on "altering the deal" for it to pass.

The Constitution is far more than a piece of paper, it's the foundation of all law in the US.

You miss my point. If the small states keep abusing their power, eventually the large states are going to simply reject the Constitution - and there's no mechanism for the small states to force it on them. In the end, it's a consensus arrangement. It was adopted back in the day in the form that it originally had, because that was the only thing that all then-states could agree on. If it stops being a thing that enough states can agree on now, then it is just a piece of paper. It doesn't have any magical innate powers to enforce itself.

The large states can't "reject the Constitution". There aren't enough of them, and the mechanism to enforce it is the federal courts, who don't care how big a state is.

Access to the courts and their attendant enforcement mechanisms is not something restricted to the large states. Agreements were made, documents written and signed, and at least one bloody war fought to preserve that "just a piece of paper", and the result has been quite clear throughout the history of this nation.