the most suited camper would be the Burstner delfin performance based on a renault 2.5 either 120bhp or 140bhp. this is a tagaxel overbed garage 2/4 berth and are a real barhin at the moment seen plenty 2005 to 2007 models for around the 39-42k mark.
not sure on the rear garage capacity try emailing burstner in Germany unless "lowdhams" know the capacity bu as kev said 2 bikes will weight at leat 300kg with fuel and thats a lot of weight on the rear axel [ the bustner has a payload of 1000kg]
how about a small twin bike trailer?
The only other good manufacturer is Dethleffs which we have and are excellent but again th max single rear axel is 150kg in the garage due to rear overhang and thats on a 3900kg chassy with a payload of 700kg.
motorcycles not for road use but to transport classic race machines between events,one a 125 ducati weighs 180lbs,the other a 250 honda that comes in at 210lbs,total for easy reconing 400lbs,converted to kgs=181.Present transport is great for me a hymer 680 twin wheel starline but joan wont drive it as she says it is to wide at the front and dashboard to long,as most race events are in the netherlands,germany,and the czech republic,we are a long way from home,please see photos,if i leg it off would be a great problem getting home.