I'll bring sluckey's TDR schematic in for reference which helps in ignoring the normal channel.
Two things Mr. Rivera mentioned in that video stand out as places I would start. Reducing bass and adding a Master Vol.
When I built my version of a TDR I incorporated the Master from sluckey's schematic (and loved it) - R7 1ooK
The more you can crank R10 the more alive the amp becomes, so the Master helps to make that manageable.
To reduce bass I would simply lower the value of the cathode bypass cap on V1-B. Personally, I would use a cap decade box to dial in the actual value rather than just pick one value and settle on it. 5uf is probably not a bad guess. C6 would be another point of experimentation...(the use of humbuckers vs. single coil pickups would come into play)
Additionally, I would have to imagine that his 6-position rotary switch involved 6 different values for the mid cap in the tone stack. The lower you make that value, the more low mids will be brought in. But, maybe his solution was just 6 different slope resistor values?
I also
imagine that some of his boost was added through manipulation of the fixed value 6.8K - tone stack to ground (R9)
If you use a pot in place of the that resistor (sluckey refers to this as a RAW control) it allows control over gain as it
slowly lift the lossy tone stack out of the circuitSorry for the guesses but they are gathered from hands on experience. I really don't think I am off the mark by much. If you search hard enough I would have to believe that some of this info is out there somewhere on the internet already.
Do you have one to mod or are you planning on building?