I use a kryptonite cable and keep the camper in the backyard. So they'd have to get through a fence, then bust the cable/lock.
This will only stop the honest crim. If they want it, it's gone. Insurance is cheap for campers.
I'm surprised my boat hasn't gone yet, there's been a few that have disappeared from my area. They simply chain the hitch/draw bar to the back of a stolen cruiser or patrol and tow it to a tilt tray nearby - never to be seen again. I read about one boat that was stolen from Medowie area, then found in WA which then went missing again and was eventually sold in QLD, only to be 'discovered' stolen after a failed payment/repo arrangement. Incredible!