The dependence of the diagonal and the power of the quadrocopter engines?

Question

Quadcopter

Hello!
I have a Syma x5 quadcopter, I want to assemble it using the same spare parts but smaller.
Actually I bought and assembled all the details, but there is no case yet. I want to understand if there is any dependence of air movement on the blades and diagonal. What awaits me if I reduce its size, for example, by half?
Now at this stage everything is assembled and working, but it has no basis, I don’t want to poke my finger into the sky and fall without a case.