Master Stoker,
My experience with Olympic competition and the WTF Gyorugi rules (which is also adopted by the National Governing Bodies), is that only the approved equipment listed in the rule book (Headgear, Chestguard, cloth, foam or vinyl forearm guard, and shin & instep guard, mouthguard, and groin guard) may be worn (newly approved hand and foot protectors, and elbow and knee pads are optional). Anything else is prohibited. For injured areas of the body, a maximum of two layers of medical tape may be worn.
See the USA Taekwondo site for description:
http://www.usa-taekwondo.us/EQUIPMENTSTANDARDS.pdf
I can see your point about some students (especially the younger ones) needing better protection on the hip. I would think this is an issue that could be brought up to the USA Taekwondo leadership as a suggestion for future rule changes. Perhaps they could pass along the idea to the WTF rules committee. However, I wonder if a seperate pad (cloth, foam or vinyl) might hinder movement for kicking as it covers the hip area. Perhaps there could be a design change in the Hogu (chestguard) itself to accomodate an extension over the hips? :idunno: It's a good question.
CM D. J. Eisenhart