That's a beautiful guitar!
I've been able to keep high frequencies more intact when I use the volume controls by paying close attention to cable capacitance and using a buffer to preserve high frequencies. I think cable capacitance is underrated. It affects high frequency signals as much as the resistance in a volume pot. This is the case regardless of whether you mod the guitar's cap.
Forgive me if you already know all the following stuff. I mention it because lots of players don't. I've reached these conclusions after 30-plus years of studio work.
A low capacitance cable will preserve high frequencies over a longer run than a higher capacitance cable, and you can hear it. The lowest capacitance cables I've found are the Van Damme XKE (22 pF per foot) that PRS offers as its higher end OEM cable, Sommer Spirit LLX (16pF per foot), and Gotham GAC-1 Ultra-Pro (21 pF per foot). You might not be able to hear the difference between 22 pF and 16 pF in a 15-20 foot cable, but you will hear the difference between that cable and a 40-50 pF or higher capacitance in a cable of the same length.
Compared to a Mogami or Canare cable, with capacitances of 40-50 pF per foot - incidentally, these are also very fine cables, I'm not knocking them - an 18 foot low capacitance cable like the ones I mentioned above will not rob your high frequencies as quickly. Alternatively, you can have longer runs with less signal loss.
The reason cable capacitance is measured referencing length is that every foot of cable adds to the cable's capacitance. The longer the cable, the greater the high frequency loss.
All you have to do to prove how cable capacitance affects your signal is take a very short cable, like a one-foot pedal connector, and plug the guitar into the amp with it. You'll undoubtedly hear hear a brighter signal; in fact, you might find it too bright!
If you're using a pedalboard, a high quality buffer is a great high frequency preservation device. Here I'm not talking about the inexpensive buffers thrown onto Boss pedals. A good buffer is a different thing. Once the signal hits the buffer, the high frequencies are preserved because the signal is converted from high to low impedance by its circuit.
The beauty of a buffer is that the cable following the buffer is far less of a problem, and the capacitance of the cable following the buffer doesn't noticeably affect the signal, except that a good cable rejects noise and is mechanically more robust. Use the higher capacitance cables from pedalboard to amp, or to amp switcher, no problem after the buffer.
I've migrated from using 20 foot cables to 10 and 15 footers. Every little bit helps.
Point is that this aspect of high frequency preservation has lots of factors.