Replaced faders with knobs. The existing faders had a pinout listed on the side, something like "1 1' 2 2' 3 3' ". I just used the same pinout on the RK27s. The small PCBs that the RK27s are mounted to were from dalaudio.com. They are terrific and inexpensive.
I didn't realize what fantastic build quality the MP24 had. Viewed in a historical context, it really was starting with the Urei and Bozak as a baseline, and trying to improve upon their practical deficiencies.
After swapping the stock TL072/NE5532s/Quad Fairchild opamps out for LME49720 and LME49740, I'd put the sound of this mixer up with any DJ mixer I've used. Before that the sound was excellent, but the sound became "faster" and the bass became less distorted after the swap. Some people do not like the LME49720 because of how bright it is but I love the clarity.