It's not as hard as you might think. If you are a Tripoli or NAR member they frequently have specific launch days where there is clearance from the FAA to a certain altitude on certain days in certain areas for this kind of thing. BALLS (a once a year event) is typically cleared to 100,000ft IIRC. Typically they're much lower though. As for "close to" these type of motors are generally very reliable and Loki does a good job with them. They also made the motors for the 108% scale Black Brandt III that flew on three "P" motors. The guy that did the Black Brandt III is now working on a FULL SCALE Nike Hercules.