Could you help us understand what the limiting factor in these simulations are?

By memory considerations alone, a N-qubit wavefunction (using 64-bit floats) uses 2^(N+4) bytes, and a N-qubit unitary operator uses 2^(2N+4) bytes. If you use 1 GB of RAM, that allows you to store full unitary operators up to 13 qubits.

If you use sparse operators to store the gates (which have a size in memory that is a constant times the wavefunction size) you can imagine doing 24 qubits.

Of course fighting exponential scaling is always hard, but I'm not sure if I understand why the limit (for a hobby-level project) is closer to 10 than 24.