Yeah 242 output is very high. You need some extra resistance on the RCA output jacks to attenuate it if you are using an active preamp.
You can by some Rothwell attenuators - try the 10DB ones first.
I did try a stronger value and cannot recommend that.
If you are set on using 242, and I personally don't think anyone should be if it doesn't work by default, I would get the AN 2 Watt non-magnetic tants installed I talk about earlier. I think they are amazing, certainly better than Takman resistors I had installed.
Bear in mind if you optimise it for 242, you will un-optimise it for everything else. That's just life, and I would personally just get it vaguely in the right ballpark so that 242 becomes usable and doesn't distort, but doesn't require huge preamp gain on tubes with lower output.
My resistors are 470K. 242 is usuable in my DAC at that value.
Another option is to get the passive Lampi volume controller installed and use that. Or use a passive instead of active pre.