Overweight is relation to height rather than age, but that really isn't an issue at all with performing "stunts". I am 175 and was in the x-games performing "stunts". The most useful "stunt" in the sport (that I can think of ATM) is the bunnyhop! This basic maneuver is the one that will get you further in this sport than almost anything else. You can get over curbs, rocks, rivers, cracks, etc. Wheelies are cool and help in skatepark contests, and for a short distance might help with getting up on things, but it is really just the first step in a bunnyhop. Wheelies are the only trick where weight can be a factor since you will be torquing your chain, but that shouldn't matter in your decision (going up hills does the same thing). Endos (stoppies) are not practical for anything I can think of except to practice front end balance. Bottom line: LEARN BUNNYHOPS FIRST!!