A great blog post here, on the effects of residual propellants and how it affects the performance of a rocket.
Residual propellants have always been something I have known and read about but never really looked into the effects off. This could be worth investigating for any of the FAR-MARS prize participants, but this would depend on the flight profile in order to hit the 45kft.
At this scale, one could burn to overshoot the mark and use drag brakes and real-time processing to hit the required altitude, as an example. Those burning to depletion and hoping for the best, this may be something to consider, this could easily also be estimated for sims by conducting an all up stack test and weighing the rocket after burnout.
Anyhow, the post is worth a read regardless.
Are you a participant in the prize? I’d be keen to know how exactly you plan to hit the 45kft altitude!