Just don't run it with 2 tubes pulled and on the silicon diode setting. With 4 tubes you are good, though there a chance of tube failure and damage to the amp. I replaced my SGR's with 5 watt resistors so I can run it safely with EL34's and the ss rectifier now, but I did blow the stock 2 watt resistors and took out a pair of tubes previously. I did run it with EL34's for quite a while before the failure though. I also run my poweramp quite hot with the masters and loop active at 3/4 or above generally, and the channel gain very low compared to the stereo typical Recto user, so ymmv.My 2 channel has EH 5U4GB rectifier tubes in it. Seems like the 5AR4 is the in-between for that and the silicon diodes. I'll start with EL34s first, since I have them.
My clean channel gain is around 11:30, and red cloned to orange vintage high gain with the gain about 12:30. I also crank the treble and mid controls, and keep the bass around noon on the clean channel, and 11:30ish on the high gain channel. Those get hit with my boosts, parametric + preamp, or fuzzes to give me whatever texture I am looking for.