Awesome work, it's looking fantastic! Looking forward to seeing how you'll squeeze the retracts in there. For the props, you might have a look at the Dynam B-26 props. I think they are the only contra rotating 4 blades out there outside of small miniquad props.
The fuselage/wing is so fat that I think retracts will actually be quite simple. Just need to make a rectangular box for them to sit in, and a simple lid. Maybe we could 3D print some hinges for that. We'll see if Sponz has any ideas, he's the 3D guy.
I more concerned about prop size than 4 blade. To be scale, at this 25" wingspan 16" props are needed lol. Wonder how big I can go with the C pack on 2s.
Just brilliant work! Did you hand cut the sub-structure pieces? The look like they are laser cut they fit so well.
DamoRC
I cheat big time. Built myself a CNC machine, which is excellent for rapid prototyping. Otherwise, all the frame pieces would probably have simpler lightening cutouts.
Wow man! Your build is looking great! Can't wait to see this one in the air! As far as how tight you can roll foam board for the engine pods....id say pretty tight. I rolled the nacelles on my little Boeing 314 project. If you look in the attached pic, you can see one on the build table next to a American flag. The diameter is about 1.5 inches. Had to make a lot of relief cuts, but they came out good. I don't think you will have any problems. Your build is really coming out great, wish I was that far along on my Spatz 
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Yeah, I've had success rolling stuff tightly in short sections. We'll see how longer pieces work. I may have to split stuff up. At least my tube will be a bit bigger. I sized the plane up enough that they're around 1.75 inches.