RE: Nacell
I am not big on 3 blade props because the 2 blade is more efficient. However if your engine spacing requires a larger prop than you planned, the 3 blade is an option. If you use a 10x6 prop and go to 3 blade,, start with 9x5 3 blade.
I noticed in the landing gear, you built it exactly like the "plan". I made that part removable. My Main gear bolts to the square box f/glassed to the fuse. belly. I used 6 4x40 socket head screws and blind nuts. This makes the plate removable for repairs/upgrades. The belly of your plane looks about the right height. Mine was lower and on grass that was a problem.
One small point,, I used 5/32 wire for the gear, and then put hardwood landing gear blocks over the struts to make the wheels more rigid. Prior to that the wires were bending on landings.
Flaps.. I use full flaps, (all I can put down) on take off. Let the plane roll and pick up speed with a neutral elevator. Then when it has speed give up elevator. I have to use full up elevator for take off and after lift off release some of the up pressure to level out the rate of climb. Takeoff's are very realistic. The nose will lift and the mains will stay planted. When flying speed is reached the mains will lift off. CAUTION, if you don't reduce the pressure on the elev (NOT PUSH DOWN) the plane will over rotate to a very steep climb angle of climb.
Landings are better with 1/2 flaps. (my full is about 45 degrees down and I only have 2 flaps / wing) I did not add the 3rd on the removable wing tip.
For landing,, I use 1/2 flaps and fly a steep almost power off glide path (vietman type approach) This way if an engine quits power is back and you can still make the landing. If your engines are really reliable and mine are, but I still fly steep you can fly a power on landing.
Now lets talk making the landing. Flaps 1/2, power almost to idle fly stable path until about 4 or so ft above the touchdown point. Then add 2 or so clicks of throttle. Once you have leveled off allow the plane to settle and as soon as the wheels touch power to idle AND FLAPS UP. The flaps up will prevent going airborne if you get a large gust of wind.
I am now doing touch and goes. At touch down I add full power then put the flaps down to full. Then add up elevator for lift off.
I now have 19 (8 minute) flights very successful. The first were shakey due to the elevator incident being too positive, but the plane is now very stable. In only 1 of the 19 flights did an engine quit due to bad fuel (new out of the jug). When the outboard engine quit the plane immediately turned to the dead engine. I mix ail to rudder. When the engine quit I added hard elevator (which also added the needed rudder) straightened the plane then flew the traffic pattern to steep final approach on 3 engines.
When you paint be sure to fill the pin holes. It is full of pin holes..
Good luck,, Jim