Yup. When I had my Mogwai SE, I got better results (sonically, noise floor) with 9 pin tubes (12A_7, 5751) over 8 pin tubes (6S_7), so I mainly used the former with an adapter. You might want to determine at the outset whether to proceed with 9 pin vs 8 pin, then determine the amount of desired gain, which will allow you to narrow down to a certain tube type(s) to pursue.
Justin offers an informative discussion about tubes including 9 pin vs 8 pin in this video. https://www.youtube.com/watch?v=0WZ95EsIEkc
I believe the key here is figuring out which gain your intended pairing needs, which is why I have/had 1 or more of each in order to dial in.
I believe the gain of 6SL7 is similar to 5751 and 6SN7 is similar to 12AU7.