Here's Vinnie's list of tested/approved tubes and settings:
Directly Heated Triode type Filament Voltage Setting
T100 (KR Audio), 5V
101D / 205D, 4V
50 (Elrog), 5V (one of Srajan's favorites for his L2 Preamp)
The LIO DHT PRE can run all the tubes above except for the KR Audio T100 (its base is too large in diameter to fit in the top cover hole).