Clecoed the upper forward fuselage. Unfortunately the firewall doesn't seem to adhere properly to the ribs. The reason is a a wrong hole alignment on the F-1044 and the underlying firewall F-1001B. The misalignment induces strong tension in the structure. Lucio suggested to modify the hole using an -08 bolt (allen socket bolt) and to elongate a bit the hole in order align correctly.
After that riveting as per plan went smoothly thanks to Lucio's help.
Firewall not riveted as i need to prepare the hinges.