When confronted with life's dilemma, one can always do the "uberwaltz" and forgeddaboudit, at least for a while.
FWIW, I wouldn't go as low as 20 ohms, even WITH a SUT. But (Madavid) keep in mind that the "20 ohms" is the reflected load, in the case where you use a SUT, not the value of the load resistor. When you use a SUT, the net load seen by the cartridge is equal to the value of the load resistor on the secondary side of the SUT, divided by the square of the turns ratio of the SUT. For a 1:10 SUT, use "100" as your divisor, etc.
FWIW, I wouldn't go as low as 20 ohms, even WITH a SUT. But (Madavid) keep in mind that the "20 ohms" is the reflected load, in the case where you use a SUT, not the value of the load resistor. When you use a SUT, the net load seen by the cartridge is equal to the value of the load resistor on the secondary side of the SUT, divided by the square of the turns ratio of the SUT. For a 1:10 SUT, use "100" as your divisor, etc.