Onestringer, if I am going to a large 3-D shoot I try and find a contact person from the club putting on the shoot. I call and ask what the rules are that day. Some clubs follow IBO rules, some follow NFAA rules, some clubs like ours make up our own by what we feel is fair to everyone.
Ibo has very specific rules for trad classes. NFAA seems to bunch everyone into one class.
Both groups have web sites with the rules posted if that helps.
Nothing worst than travling to a shoot and finding out that your bow or arrows are not legal. It does not make for a "happy bowshooter". I know from experience.