Are you aware that the frequency response can significantly change when you turn up/down the guitar volume and even the tone knob?
That actually has no effect on the accuracy of an EQ match. Check out this demo. The first sample you'll hear in the demo is the original source with the guitar volume all the way up. The next sample is the Tone Matched version with the guitar volume also at 100%. The series of clips after that follow the same pattern but with the guitar volume rolled down progressively lower with each subsequent pair of samples.