Your approach in the pictures will work just fine. The fuselage on this particular model has the roots molded in at the proper angle. Just block it to where the Robart reads 0 and put the firewall in at 90 degrees to the table surface. Set the horizontal stab at zero zero with the wing panels and balance it at the tick marks molded into the root fairings.
It is a very neutral flyer upright or inverted. It is just a touch squirrely on take off as there is a point where the tail wants to lift before the vertical fin and rudder become fully effective. In flight it grooves and is scale aerobatic capable.