I bought the MA240s in "kit" form from Ralph back in the late 90s. My pair were among the last ones he made, and I wanted to assemble the circuit such that each 6C33C could be separately biased, which required 3 separate driver tubes, one for each pair of output tubes. At that time, I knew very little about circuit design or tubes or how to read a schematic, even. But I found a local guy who put the amplifiers together for me. (MA240 essentially equals an MA2 with 6C33Cs instead of a gaggle of 6AS7s.) Then I started studying tube electronics from books and with input from anyone who would talk to me, including a lot from Ralph. Over the years I have made many further mods, including I have now reduced the output tube count by using four 7241 triodes per channel, instead of six 6C33Cs. Gives about the same power but requires fewer tubes all around. My Sound Lab 845PXs are modified as well. Sorry for off topic.
I don't think your problems with RFI are likely to be due to something in the MP1 circuit. Ralph makes a point about the fact that his units are relatively cable insensitive. I've certainly never had a problem with hum or RFI, and I don't use megabuck cables; I make my cables in fact.