2826 versus 2820?
I would say it comes down to what your AUW will be.
I have built two of these, from the original version. First was an ARF, and was fairly light so could have used a 2820. But I flew it with an AXI2826
Second one was an ARC, but was much heavier. I think a 2820 would be have been pushed a bit too hard.
Assuming CG is correct the extra ounce of motor weight won't matter to the plane, but will allow for more power to be produced by the motor without overheating.
Originally I had a 2826/10, 12x6 APC on 4S TP2800. Based on the first one I made the mistake of shortening the nose, and ended up needing quite a bit of nose weight.
Now it has a three blade 11x5 "Igor" prop, which requires a bit more power so it has 5STP2800. Motor is a Orbit 15-20, which avoids any motor resonance problems.
(I tried an AXI 2826/12, but the flight RPM was right in a bad resonance range for the motor. Could have been bad bearings, because Igor gets away with it.)
So if you have a suitable 2826, I would say use it.
Due to the shortened nose I had to make a balsa hatch. First one was similar, but used the fiberglass hatch.
The little baffle is made from Depron, and ensures most of the cooling air goes to the motor, with a small hole letting some go directly to the ESC.
The only air exit is on the underside of the fuse, between the wing and stab.
Pat MacKenzie