tryst or trysting

[angliholic]

One could reason that there was legitimate public interest in the kind of trysting/tryst that might cause emotional problems if any combination of these astronauts might be together in space.

Which should I use here, trysting or tryst, and why? Thanks.
Does trysting or tryst mean dating covertly?

[Tdol]

The noun sounds better to me. A tryst doesn't have to be covert, though it often is.