Splais.....Large commercial aircraft use the Fuselage Wl to compute wing/stab incidence....the stab is fully trimmable for both "+" and "-" degrees of incidence......its important when building a model to determine what reference one would like to use for setting up wing/tail incidence......they both have an important role on how an aircraft will fly.......I like Nick Zirolis way of using a "Crutch" system to build a model...it gives me a Wl to refernce the wing/tail incidences....for example if I set the crutch @ "0" using an incidence meter then all my wing/tail measurements will reflect a"+" or "-" from that reference point.....different models have incidences that reflect their own individual flying characteristics......The "+" or "-" is used as a description of where the Leading edge of the wing/tail is in relation to the fuselage reference point...... with the smaller models changing the wing/tail incidences are fairly easy to accomplish...the larger giant scale models its best to make wing/tail incidences as described by the plans designer....Bill....