Over the course of many years Jean Wantzenriether has developed and published an approach to trimming and design modification of high performance rubber powered free flight models. One key aspect of his method is to avoid the use of variable position surfaces except for de-thermalization. The name first given to the method was PGI, standing for Piqueur Gravite' Incidence which refers to the key aspects of thrust line relative to the center of gravity, center of gravity location and wing incidence relative to the thrust line. Later refinements and additions to his method led to the name TOP, for Three axis Optimal Permanent equilibrium. TOP, like PGI, avoids variable positions surfaces. TOP additionally provides guidance effecting both the lateral axis and longitudinal axis.
Starting around 1980 Jean's publications on PGI and TOP have appeared in many places such as Vol Libre, The National Free Flight Society Symposiums, and Free Flight Quarterly. "Insights on the Dynamics of Rubber Powered FAI models", a book published by Free Flight Quarterly, contains a comprehensive overview by Jean of PGI and TOP. In this book one can find not only the PGI and TOP methods, but also other extremely interesting analyses of the design and operational aspects of a contest rubber model, in particular the role of the horizontal stabilizer and on optimum propellers. "TOP Fundamentals" an article from this book may be read by opening the following link, TOP Fundamentals . Additional information on the book and how to buy a copy my be found at FFQ Books .