You want to spawn the Metal Clip tanks use on custom models .... i often wondered if that was possible myself when i spawned tanks in stock maps ... if i remember right you can only use them if they were added by the mapper when making the map (theyre usually hidden in the map somewhere), i only ever found one that wasnt used but it let me spawn a truck with a metal clip once i found it. You can of course use them as many times as you like but using them with custom models ... the shape/size would differ to your new model.
Is it possible to spawn the metal clip ... im not sure, tried myself but failed all those yrs ago lol.