The Don Smith Plans I have do show the engine installation, a couple of 3W 24's I believe, placement of servos are your choice, He did answer my emails, I got the canopy and both cowls from him and Century Jet makes a custome set of retracts - last quote from them was $419.00 US a year or so ago - maybe more now - they never seem to go down !
The Al Masters plans are more detailed and are answer more questions, but if you have ever scratch built before the Don SMith plans should not be a problem.

Wing loading on the Al masters was not a problem, this A/C has a huge wing - more area than most twins of the same WS, the flaps work beautifully - no pitching - it just slows down as you deploy them. I built and flew the smaller Al MAsters DO335 with a ys 45 in the front and a .25 in the rear and that was obscenely over powered - can't image it with a couple of Saito 4S - YIKES !
Its only rated for two .25's and the YS could fly it just fine by itself.
The 80" one flies well enough on the YS 120.