As above - I have a little trailer with matching wheels but had to get the centre machined out to fit the hubs.
With the Trak Shak camper, I didn't bother and have been all through the Red Centre, Vic High Country, Flinders many times, and never had a puncture.
I know it's good to have matching wheels for spares but buy good tyres, have a tyre pressure monitoring system (I have the Tyredog system), reduce your pressure on dirt roads etc, and you should be ok.