Would it be possible to set up a balance in the gate, with one arm in, and subject to the gravity of, each world?
Not really, in the current version the gate is a painting of a location on the
other world, and a specific spell instantly transports the persons in front of
the painting to the location the painting shows, so it is now more like tele-
portation than like a typical gate or portal.
As for the gravity thing, after some more thoughts I have com to the con-
clusion that I will give the characters some hints, like the increased range
of a crossbow and such, but that I will leave everything else (the idea that
it has to do with gravity, potential methods to determine the differences in
the two worlds' gravity fields, etc.) to the characters.
Good ideas will be rewarded with significant improvements of the relevant
knowledge skills, if the characters ignore the hints and the problem, some
non-player character will have the right insight - and the reward - later in