Hello Flyboy!
The problem with GPX files, is that they do not contain any roll/pitch/yaw information. In that case, Tacview must guess, and tries to display something which make sense for a normal flight. Obviously, this does not work so well for something more complex like aerobatics
I know that some high-end Garmin GPS can output additional formats like csv files. They contain much more information, including full aircraft orientation. Does the Virb can output other formats than GPX files? Can you share some of your data? This may help me to improve the actual support of real-life telemetry.
Now, for the plane shape, I have just added the 8KCAB to Tacview 1.7.4 database.
Until this version is available, the simplest thing to do on your side, is to use the edition tool ("Edit Selected Object") and change the aircraft name to C-152 (this is the closed type I can think about). This should display a C-152 3D model in place of the default model. You may also want to switch the object type to “fixedwing”.