Beartums,

Heat doesn't rise, HOT AIR rises. That is why a hot air balloon works.
Half of the heat from the radiator is convection, the other half is
radiation. The convection part will heat the air next to the radiator,
which will rise up to heat the cold window above it. The radiation
part will heat the entire room, including the sunken floor. Your
current configuration should work fine, as long as the radiator is
sized right.

Stretch