The aft block, (that comes in contact with the stab) at the rear where it hits the stab, is shaped on the bottom to conform to the stab's airfoil. I added my aft block before adding the vertical fin, and cut a center slit in it to accept the fin. Make sure your top block is nice and rounded...and corresponds to the side view of the plan.

As for the rudder posts that extends down, I believe you can add a bit of soft balsa to each side and sand to make smooth. In general, I like to sand as much off as possible, while still leaving structural strength.

We made two hatches, (behind the firewall, for access to the fuel tank area, and a second for radio access). The fuel tank hatch isn't absolutely necessary, but I prefer open access. There is adequate strength there. The fore-top block should be trimmed to meet the plan side view and top view. Be sure to sand to pick up the angle. I sand away a LOT of the fore blocks to make a trim nose section.

Hope this helps

Duane