[Jenibelle]

Normal dominance behavior. They're in a new home, so they need to figure out who is really boss. They were also introduced to a new playpen.

Chasing, humping, teeth chattering, even nipping are all completely normal. Unless they draw blood, don't separate. It may look scary to us but it's normal to them.

Only separate for blood or if you catch them in a fighting stance.
Fighting stance: nose high on the air, mouth open, making a LOUD chattering noise. They will be facing each other, squaring up. If this is the case throw a blanket on them to distract and separate.

I don't want to sound like a broken record, but honestly if they keep it up more space as soon as possible is the best solution. I know you're planning on upgrading though! ^.^