You are now reporting that you achieve unity volume level at about 3:00 o’clock on the Volume pot. Setting both Gain controls at max should produce unity level near 2:00 o’clock. So, you are not that far off from the expected results. I suggest you try adjusting all three trimmers to increase the output of the transistors. As long as you can achieve unity level, you are achieving the desired results. The SUNN T is primarily designed as a tonal modification device. It was not intended to be simply a volume boost. I think you are close to achieving the desired tones.