Launched at FireBALLS-005 in August 1995, Project 463 was the biggest sport rocket ever flown at 42' and 1200 lbs. It flew on a P and 2 N's in the booster and a single N in the sustainer, although the sustainer didn't ignite. This huge project was built by Chuck Sackett in his Florida shop. It featured a lot of sonotube (up to 3" in diameter), several aluminum plates and tubes, an internal steel framework, and piston separation. Moving this monster must have been quite a feat. But not as difficult as erecting it. The EX motors were built by his pal Mike Ward. These two also conspired on what was previously the biggest sport rocket, the Down Right Ignorant. I embedded a video (hat tip to R2K) and several screen snaps (via Point 39 Productions).
Heck, while I'm at it, here is the launch of the Down Right Ignorant