The initial plan back than (around 2014) was to build a rocket that can exceed 40km. It wasn't hard to convince the other team members, that 42 is a much better number.
Simulations indicated early on, that more is possible with the basic concept. For most of the time, this wasn't publicly announced. Earlier released simulation plots contained significant ballast to keep the "official" altitude low. Personally, I would have preferred to stay with the 42km+ story on the outside, but I'm probably a lousy PR person.
From a mass fraction/performance perspective, I don't think the goal is completely unrealistic. But there are countless things that can go wrong during flight, especially if the envelope gets pushed and related experience is rare.
Historically speaking, these kinds of projects are not very successful. They are interesting though and I finally have a good excuse to attend BALLS
.
Sorry for hijacking the wrong thread. I should start a new one, but currently I don't have too much time.
Reinhard