Or how about this for a solution. The start cylinder has a top, right?
It actually extends well beyond the boundary of the cylinder. If you
go above this top, you must come back below it and remain below it for
two minutes before you can get a start without incurring a penalty. We
all know the rule.

How about a similar, but inverted plane and system at the base of the
finish cylinder? One data point below the base of the finish cylinder,
and you cannot get a finish until you have been above it for two
minutes. Or, maybe make it five. Might as well go take your rolling
finish if you dip below it on final glide. It is much easier to apply
the same rule two different places than to try and come up with
something else, IMHO. Will certainly stop ballistic trajectories, but
not the level decel.

Don't get me wrong, John. I like donuts, but in the morning before the
Pilot's Meetings!

Steve Leonard
ZS