I am a fan of the GG as well. It came with the standard KR5U4G and 242KR tubes. I have WE422A and 274B To try also. Although I haven’t been a fan of the 274B I’ll try it. I’m also going to install a quad of TFK RS241/242 and WE101D from Psvane. We can tube roll when you visit. I am going to part with the rest of my tubes I’m not using before I move. I did sell a ton of less valuable nos tubes and kept the rest - TFK AD1, RGN2504 mesh etc. for future projects. Apparently the future is now and I don’t have the energy or desire to build more amps.
Dude you are my hero. The 242 is by far the best and I want to hear it on a good horn. I also want to compare the telefunken to the KR.
I would say don't sell all the others because the 242 with Lampi is finicky that if you ever change your preamp it might not work. So if you ever get the urge to change downstream or try different stuff it is good to have a couple of the other tubes on hand.