@atmasphere My tech said this about the ST-35 mods we're discussing:
"The datasheet lists a 10k plate-to-plate load for the tubes in triode mode and 8k plate-to-plate in ultra linear, so it's not that far off. Per the Mullard datasheet, power drops to about 5W, which is expected. Full power distortion is ~2.5% vs 1.17, but probably lower at lower power levels. Required grid voltage is about the same, so the feedback probably won't be completely borked. As for more gain, short of building a new amp on a new chassis, that is not an option and of course it would no longer be an st-35."