Three comments here:
1. Once you modify stuff, the value usually goes down.
2. Ralph’s stuff on the resale market sells pretty quickly
3. Ralph’s stuff on the resale market holds its value
Even if wood or glue or other things would improve the sound, why would you take the chance?
Having heard Ralph's amps at the Florida Audio Expo, I wouldn't touch them...well, except to plug them in, turn them on and enjoy!