Small guitars? Check your pans first.

Before you touch an EQ, check where your rhythm guitars sit. Two separate takes of the same riff, panned hard left and hard right, is where the size in a heavy mix comes from.

The two takes in the video are close but not identical: their left-right correlation measures 0.418. That difference is what your ears hear as width. Stack both in the middle and the vectorscope collapses to a line: same notes, same loudness (we matched them), no size.

It has to be two real takes. Copying one take to both sides won't do it. Identical left and right is just mono, and the scope still shows a line.

Next: Where your low string actually lives.