Here is something I have been meaning to post for a long, long time now. It's a technique I have used to simulate frames, stringers and longerons inside fuselage halves. Using a product revealed to me during my college days, zipaline, which is basically adhesive tape sold in a series of very thin widths, I just lay down the horizontal stringers and longerons and overlay the frames on top of that. No glue marks, repositionable and easy to overlay other tape strips. Extend past the fuselage while laying the tape down and trim after painted (to seal in place). Easy peasy.
...or I guess you could just cut thin colored tape into strips of varying width.